There are a few of us doing the foam scratchbuild thing throughout the island. The group I fly with (Arecibo/Los Pinos) is very active with "scratchbuild" foam and electrics. We started with the RC Powers designs but we've transitioned to other designers like FRC Foamies, and others. I'm currently cutting my first Flite Test plans; an FT3D and FT Cruiser for myself and an FT Dusty for a friend. One of the guys in our group has even started doing his own true scratchbuild foamie (non-plan based) designs. There are also individual flyers doing the foam scratchbuilt thing at the Moca/Labadie club near where you live and in the other clubs throughout the island.
At the Arecibo/Los Pinos "club", we flow mostly off grass but we use the access road as a runway (beware of the plane-eating curbs). We're able to use the access road because it's only used by us and a handful of employees of an incinerator that is down the road from us. We're not a formal club so there are no dues or membership fees, and the group welcomes anyone to come fly with us. We fly in an empty industrial lots in the Santana Industrial Park (next to a pacemaker factory/incinerator/AEE warehouse). We usually meet Sundays after 1:00 PM. You can reach the field from Road #2 entering by industrial lot of black plastic drainage tubes; not too far from the Arecibo Airport and next to "Urbanizacion Los Pinos". Since we're near the airport we usually have to keep below the 400' altitude but that's usually not a problem with the planes we fly there. The local airport knows about us so and some of the local (real aircraft) pilots even fly RC with our group.
Regarding the foam... None of the local Hobby Shops in Puerto Rico seem to sell Depron or EPP foam. Some of the locals that build with foam use foamboard bought from Walgreens, Walmart, CVS or OfficeMax, with and without paper removed. The brands of foamboard I've found locally are the types that have the difficult to remove paper. I did my first builds with foamboard but I didn't like the weight penalty and it was too much work to remove the paper so I started buying foam by the case or half case (20 or 10 sheets) from rcfoam.com. The shipping is $30-40 per case but I resell some of it to other locals at cost (sheet cost + shipping). The price per sheet is between $9 and $14 depending on the size of the case I order and the shipping cost of the particular order.
Once I run out of the current case of Depron I have in-stock, I'm going to order a box of XPS foam (same foam as Model Plane Foam/MPF) from RC Foam. If this foam works well, it will cut in half our cost per sheet. Due to USPS dimensional shipping rules, the cost of shipping is almost the same if you order 1 sheet or 10 ($30+). RC Foam quoted me $13.99 shipping for the 16 sheet case of XPS foam but I wouldn't be surprised if that's a shopping cart error and they latter come back with a higher shipping cost.