Hi Jaguar - there are some great Texas Fodorites that will help you for both cities. I have only been to Austin twice, but am happy to share my recommendations. I am not sure on the 150.00 per night - I stayed at the Courtyard Marriott & the Residence Inn in Austin. I recommend either property. If you can get the Residence Inn stay at that one - as breakfast is included and it was more "updated".
Have fun!

We stayed at the Residence Inn in San Antonio and it was great. You could walk to the market place and take the trolley to the riverwalk. It is nice to have a suite and the breakfast and afternoon lite suppers were great.

Checking hotels.com, there are several Riverwalk properties with rates in that price range:

http://tinyurl.com/8gg5v54

Do you just want a place to lay your head or do you want something upscale, or with character? The Menger has good rates and is a historic hotel (built in 1859). http://mengerhotel.com/ Another historic hotel is St. Anthony.

If you just want a place to sleep, we like Embassy Suites and they have good rates for February: http://www.embassysuitesriverwalk.com/

(fyi, I live in the area and have not stayed at these hotels)

We like the Marriott Rivercenter in San Antonio, not sure of their prices since we usually stay on points.

We have stayed at the Marriott Rivercenter but it's at least $250/night at that time. It'd be great if you could find a special.

Thanks for your suggestions. I'll check these hotels out and see what the prices are.

I've had a quick look at San Antonio hotels. The Marriott Rivercenter has no rooms available (we're staying at the weekend so maybe that's why). The Residence Inn is $372 and the reviews are mainly good. I see the Hyatt Place North/Stone Oak is given excellent reviews and I can get 2 nights for just $263 with free parking and breakfast too. But maybe it's a bit far from the Riverwalk and Alamo? The Best Western Sunset Suites has excellent reviews too and will cost us $321 and also has free parking and breakfast, just 2 blocks from the Riverwalk. The Embassy Suites price is $312 but the parking is expensive. By the way, I was checking for King rooms.

San Antonio downtown hotels can be pricey. If you're going budget-buster (way off your $150/night), I recommend La Mansion del Rio. It's historic, right on the river, and they have a fantastic Sunday brunch, if you'll be here on a weekend. That said, there are some budget-friendlier options. For B&Bs, I would look at the area called "Southtown" and/or "King William," just south of the downtown area. You'll be about 1/2 to 1 mile from the main part of the river, but it's historic and very walkable. There are a couple of B&B options that wlll get you closer to your budget: A Yellow Rose and Brackenridge House. In between the main part of downtown and Southtown is Arbor House Inn. There are lots of good restaurants in Southtown, you're within a mile or two of most of the sights you'll want to see downtown, and I'm sure your inkeepers can point you to the trolley stops. Another option is Hotel Havana, which is to the north of the downtown core, but still on the river. The river is curved like a snake and zigzags back and forth through the main part of downtown. Stone Oak is about 15 miles away from the center of the city, and you'll have to find parking when you drive in (as much as $15-20 for the day). San Antonio downtown is not easy to navigate, as there's not a grid system. The main arteries are more like spokes of a wheel. To get the most out of your two days and limit frustration of driving in a quirky city, I recommend parking your car.

We have always stayed at the Menger Hotel. It's right by the Alamo and a very short walk to the Riverwalk area.

http://mengerhotel.com

We've also stayed at the Crockett Hotel. Also near the Alamo and the Riverwalk. These are both historic San Antonio Hotels.

http://www.crocketthotel.com

The Menger will charge me $386 including parking, the Crockett $317 including parking and a free breakfast. There's 'no room at the Inn' as far as the Yellow Rose and Mansion del Rio are concerned. Looks like it's a toss up between the Crockett and Best Western Sunset Suites. I'll check out the Austin hotels next - an earlier search I did for Austin shortlisted the HILTON GARDEN INN NORTHWEST ARBORETUM. 2 nights in a king bed for $363 (free cancellation). But maybe that's a long way from anywhere interesting.

We're staying at the Star of Texas B&B next month in Austin. It fits your budget of $150 a night. They also have a sister B&B Austin Folk House.

Other than price the other important thing to consider is what you are interested in doing while you are here. If you want to catch great live music, which you can do every night of the week you should check out San Jose on S. Congress. The hotel is lovely and very Austin, and right across the street from The Continental Club and surrounded by lots of things to see and eat. It's also close to Town Lake if you want to go for a run and downtown. San Jose is in South Austin. Another great option and less expensive is to check out airbnb.com for places by owners. East Austin is also another great part of town to check out for clubs and music. I mean East of I-35. Stay away from E. 6th that is West of I-35 unless you want to be surrounded by drunk young idiots and girls running around in wedding veils going out on the town in too short of a dress for a bachelorette party. The Warehouse District (E. 4th) and 2nd District are also good places to go to, but the W is an expensive hotel. Don't forget to check our fabulous food trucks especially East Side King (at three different bars on the east side), which are run by the recent winner of Top Chef.

What are your dates? I priced Feb 21-24 and got $127-149/night at Menger. Standard queen bed, best available rate, $152. You can do better if you have AAA or AARP>