We didn't have a destination wedding, but we did a rehearsal dinner/welcome dinner combo because the majority of our guests were travelling from out of town. We had between 70-75 guests in attendance at the dinner the night before the wedding. We were able to keep costs down by renting a party room, having a caterer do heavy app stations, hiring some students to serve as bartenders, and DIY-ing the decor. The whole thing came out around $3000, which was very reasonable for us. If you can try to DIY part of it, that would be a good way to keep costs down (though that might be difficult if you're having a destination wedding in PR). Maybe contact some more casual restaurants nearby and see if someone can offer you a package deal, or something with heavy app stations instead of a full sit-down meal.
My ILs hosted our rehearsal dinner in their apartment. Do you live in the area, or will you have access to a kitchen? Rehearsal dinners don't have to be decorated, fancy, or anything other than yummy. Ours was super low-key and fun, with simple dishes like pesto, chicken cacciatore, pork loin, and homemade chocolate cake (made dairy and gluten free for certain guests). At this point I should mention my ILs *are* Italian-American.
But, as mentioned above, it could really just be pizza and beer.
Our Rehearsal/Welcome Dinner was in Southern California. We originally were planning on doing something low-key and inexpensive like a food truck at the hotel most guests were staying at( but my in-laws suggested having it at a nearby brewery (Stone Brewing in Escondido). It ended up being about $12k for 80-90 people. This included an open beer/wine bar.
However, I agree with PPs. The Rehearsal/Welcome Dinner doesn’t need to be fancy. I’ve been to one held at a local Italian family restaurant and another at a BJs restaurant.