Hey man, if you are looking for a recording studio here in Santiago the best one I know of just closed up and left town.
There are a few others still going though but I can't recommend them, mostly using software based systems, mixing in the box, etc. Generally in Santiago the studios will be geared towards recording traditional Dominican music and/or Jazz and so there's not alot of savvy for handling loops and things like that, but I assume since its rap that you can handle your own loop construction and your just looking for someone to slap vocals on, right?
Even at that you are going to find few studios with proper mics and vocal booths, a cardboard refrigerator box for the vocalist to stand in and sm57's/58's are going to be the norm.
If youre still interested PM me for contact info on the better ones.