The problem might not be your "signal strength", but more so you're one of many guys attempting to do the same thing.
Sounds more like the pipe is clogged up a bit with so many different users attempting to access the wifi point. Think of any free wifi service in a public place, you're not going to get upload/download speeds at any consistent high rate due to the high number of users on the same service.
I guess the question is:
Are you reliably connecting to the wifi access point? If so, are you just not experiencing the upload/download speeds you'd like. If the answer is the latter, then you might be S.O.L.
Signal strength is not indicative of the speed at which you're transmitting/receiving. It just tells you whether or not you're reliably connected.
IMHO.