At this point since he is married to the lady, the fiancee visa is out of the question and he needs to apply to bring in his wife, which I understand can be easier ( some say) or a lot harder ( others say) as they seem to criticize the legitimacy of a marriage outside the US than bringing a fiancee into the US then marrying within 90 days.
Raylusion: unless you are really hard up for money - go to an immigration lawyer in PR ( who will no doubt know a fair bit about Dominican-American relationships) and get advice on the forms, processes and waiting times. I suspect you will be spending the better part of a year doing this, though at least you can visit on a 1 hour flight more easily than a mainlander.
You have your work cut out doing the marriage thing - how long were you a couple before you got married? The longer the better. Start saving all the photos, bills and proof of the times you were together, phone records, etc., they look at all this stuff to see if this is a DR girl trying to get into the US, to then leave or if it is sincere.
And haitanbeisbol is doing what we've seen some other newbies do - post for the sake of posting whether he has a topic, knowledge or advice to offer.