There are plenty of gorgeous areas for biking in the Phoenix area, but riding in the streets isn't recommended as there are few adequate bike lanes in the city.
Phoenix Parks and Recreation (602/262-6861. www.ci.phoenix.az.us/parks) has detailed maps of Valley bike paths.
Note that the desert climate can be tough on cyclists, so make sure you're prepared with lots of water.
Pinnacle Peak, about 25 mi northeast of downtown Phoenix, is a popular place to take bikes for the ride north to Carefree and Cave Creek, or east and south over the mountain pass and down to the Verde River, toward Fountain Hills. Scottsdale's Indian Bend Wash (along Hayden Road, from Shea Boulevard south to Indian School Road) has paths suitable for bikes winding among its golf courses and ponds. South Mountain Park is the prime site for mountain bikers, with its 40-plus mi of trails -- some of them with challenging ascents and all of them quiet and scenic. Tempe Town Lake (southwest corner of Mill Avenue and Washington Street) has 5 mi of paths for skating, running, bicycling, and walking. Trail 100 runs throughout the Phoenix Mountain preserve (enter at Dreamy Draw park, just east of the intersection of Northern Avenue and 16th Street); it's just the thing for mountain bikers.
Several area adventure-tour outfits will pick you up at your hotel, supply the bikes, and take you out for excursions at different levels.
ABC/Desert Biking Adventures (602/320-4602 or 888/249-2453. www.desertbikingadventures.com) offers two-, three-, and four-hour mountain-biking excursions through the McDowell Mountains and the Sonoran Desert.
AOA Adventures (480/945-2881. www.aoa-adventures.com) leads half-day, full-day, and multiple-day adventures, with their extremely knowledgeable and personable staff.
Wheels N' Gear (16447 N. 91st St., North Scottsdale, Scottsdale. 480/945-2881) rents bikes by the day or the week.