OK Pipes, here is the deal - forget a house, especially in or near San Jose - many reasons; chief among them is it will be difficult to fit all in one place. (Even though as you get closer to leaving, I suspect the 10 to 12 will likely be more like 6 or

.
Houses w/ pools are not common, plus no one knows the place and coordinating activities is not easy - also - despite what you may have heard, you don't call up and order girls like room service - thay are unlikely to just go with you with the chance someone might Phuck them and pay them. I supose you could go to the popular venues and have guys choose, but ...... Trust me, so far all of what you are thinking sounds good but is no so good in reality.
So what to do......
I like the suggestion regarding the White House (or the Bachelor Mansion, or whatever they are calling it this week) Beautiful place; pool, in San Antonio de Escazu, above the city, beautiful air, beautiful views - but it can be cool due to the elevation - they would be able to assist you with tours, et al - put this on your list but talk with someone at the hotel before you book.
Stay in San Jose - not prettty, forget pools, but if your group wants pu*sy (and thats the problem w/ a group; some are going to be "hard core" others will not be - its why traveling with a group can be like herding cats). Check with Boyd at Hotel Little Havana - they can do tours out of there, etc - but they can also coordinate great phucking - you know your group - I've travel w/ 8 guys where only 2 phucked - as well as 4 guys when everyone did - easier when all are on the same page.
A lot depends on how hard core you group is or is pretending to be - you also could do a search since this topic gets discussed frequently.
Just curious - what happend with the last bachelor - did the wedding not take place?
Also think twice about going out of your way to be the coordinator - its a thankless job - or can be depending on the jack off level of the guys in your group (and unless you have traveled with them, you really don't "know") Personally, I'd just get a place - a hotel, not a house - and leave it at that - I'd also - even if you don't stay there, let Boyd help you at HLH w/ the Bachelor Party.