I was there in march and as much as I enjoyed my stay at the castillo , I wasn't impressed with Sonny's at all.
The total " bar area" is approximately only 20' long and 10' wide, the TV's are small and fuzzy. As far as the food goes , well it was ok at best in my opinion.
It really depends on what your looking for, if you just want somewhere to relax " by yourself" and grab an imperial for 700 colones and enjoy a nice brezze then you may like it.
There may be a busy time but I didn't see it during my stay but to be fair I never stuck around for happy hour either.
I can't imagine it being a " chica " hangout at anytime during the day or year for that matter.
They also have a very limited supply of liquor, they looked at me like I was from a different country when I asked for Jager

, all in all the people at sonny's are pleasant and everything was clean, the service was good, but atmosphere and selection is awful . But thats just my opinion and I've only been to SJ once so take it for what its worth.