Yes, the Arenal area is great. If you stay in the area, you can visit Tabacon; Eco Termales is also nice. Silencio del Campo is a popular place to stay if you want to check that one out. We also like the Lost Iguana if you want a jungly feeling. You can kayak at Lake Arenal; there's also kayaking at the Springs Resort and Spa at their Club Rio. We haven't found good snorkeling in CR. We've always felt very safe everywhere that we've gone. I wouldn't drive between cities at night though just because the roads are rough and not always well marked. Never leave valuable in your car unattended.

Costa Rica is relatively safe to explore on your own, you should just be a little careful in the big cities (San Jose) at night. And the price level is normally higher than in neighbouring countries, I don't know how much semana santa matters in that respect.
Nice spots on the west coast are the National Parc Manuel Antonio near Quepos, the peninsula Nicoya (Montezuma - beach resort for surfers&alternatives) and National Parc Corcovado. In the center, you have Volcano Arenal, National Parc Monteverde. On the Pacific Coast, the only place I can think of is Turtuguero, but it only makes sense to go there during turtle breeding season which starts about July.

We've been several times, and ditto the above comment about Manuel Antonio, Quepos and Montezuma! The best places to chill, you can hit Jaco between the two. Although they look close together on the map and its safe to drive, the roads are narrow and there are alot of slow trucks, cars and farmers.
We stayed in Arenal on another trip at Baldi which was AMAZING, something like 27 pools or various degrees and incredible gardens. Even if you don't see the volcano, its an experience.

Thank you for your help. I like the idea of chilling in Montezuma. Is there enough to do there for one week? Is it too much travel time for a one week stay in CR to try to do both Arenal and Montezuma?

You could do both in one week. Most people usually stay about three nights in Arenal; we love it there so we usually spend four or five. Have always heard good things about Uvita and Dominical, but haven't been there yet ourselves.

I definitely think we would love Arenal for the adventure but would like to balance our trip with chilling on a beautiful beach and mingling with the locals...heard uvita is awesome but would love any other suggestions on a great beach area to stay for 3 or so days..thanks so much for the help!!

The only beach area we've visited is Manuel Antonio. There's tons of wildlife there and a beautiful beach inside the park, but if you want mingling with locals, I'd lean towards going somewhere else. It's very nice but touristed, and we thought it had kind of an American feeling to it - lots of American restaurant and hotel owners. In addition to all the suggestions above and Dominical and Uvita, lots of people seem to like Puerto Viejo, Samara, Nosara, and and the Flamingo Beach area. I hear good things about Ylang Ylang since you asked about Montezuma; lots of people seem to enjoy staying there. Mal Pais is another one.

Thanks for your help. Definitely set on going to the Arenal for a few days and then off to a beach town for relaxation. Has anyone heard good things about the Mountain Paradise Hotel near Arenal. The other spa/resorts seem too pricey and I am looking for more a moderate priced hotel which is NOT all inclusive. I have also been checking out the Montezuma region. I liked the Ylang Ylang hotel but appears to be an all inclusive which is not our style. Think Manuel Antonio area seems too americanized. Any other hotel suggestions for Montezuma region or another laid back beautiful beach area to relax? Thank you for all your help. This is all so overwhelming!!

Arenal & Manuel Antonio. A great and popular combo. A good intro to the country.
We spent 8 days between the two and had a teriffic time.