I'd say half of condos in Jaco will allow guests BUT you for sure want to ask up front before booking because there are some who will not under any circumstance. If you go through a broker like Anywhere Costa Rica (
http://www.anywherecostarica.com/) make sure you are up front about guests with them as well as they might try to change you to a different condo in some cases. I have yet to find a condo complex in Los Suenos that won't allow guest. One caveat...even in condos that allow guests, sometimes there are strict rules about where guests are allowed (not around the pool) and/or what times they may come and go (usually dusk to dawn).
Two of the most popular with my clients outside the Vista Mar are Diamante Del Sol and Monaco.
http://daystardiamantedelsol.com/http://www.jacomonaco.com/Just back from three days at Vista Mar and I can't recommend those highly enough. Great security, privacy and right on-site at the Cocal not to mention in the dead center of Jaco. If the price is even close, I'd go Vista Mar every time.