no need to go all the way to Dominical, it would take you about 8-10hours. There are plent of place close to Tamarindo to explore, Negra, Avellanas, Nosara, Samara. You are going in the dry season, so don't be scared to cross rivers if that is where the road takes you, yo will find some nice secluded spots. Hopefully you have a 4x4. I just remembered too, you are going for Spring break, is your around Easter? if so the whole country goes on vacation to the beaches, I went to Avellanas to camp that week, it was soooo hot and soooo crowded, around little Hawaii there were a dozen+ people on a week peak break, so in other words you will want to drive around and explore. It will be worth it and fun too.
I went to Playa Grande from Dec. 13th, 07' to Jan. 14th, 08'. Place ruled... not built up like other cities and such. Everyone there pretty much knows everyone and they are SUPER friendly!
The owner of Las Tortugas is kind of a whack job but pretty nice none the less. You have to most definitely go to Playa Grande Inn. This couple from Florida sold off everything they owned and purchased this hotel right there and are not living there full time and running it. I forget their names now, but they were really nice and awesome to hang out with. If you do go to PGI, definitely mention my name, Mike from NJ. There was 5 of us that went there pretty much everyday and became friends with them.
Pretty much every place around there has great food and its all within walking distance. Let me know if you want to know anything else about PG.
tamarindo is a lot of fun. surf can get quite good at the rock there on the right swell, lots of local tico's all over that place though when its on (and even when its not). grande is pretty spread out, so even when its crowded you probably will find some peaks to surf on your own. but i've been on 4 different trips to the area over the past 5 years, and have only seen grande really good a handful of times. some of these places are pretty tide sensitive, so local knowledge is key. There is much partying to be had too in tamarindo, if the surf's down you definately have a lot of nightlife options going on over there you can really get carried away with that whole aspect of the trip if you let yourself
costa rica is always a blast. my favorite times have been just trunkin it in fun surf all day long, and watching the sunsets with a couple of cold ones and gettin to bed early to score the dawny the next day