Dress in whatever you feel like but realize the following:
If you dress better, it's likely that you will get better results.
One caveat might be the that you should dress to fit in but dress a notch better.
For instance wearing a tux to a frat party is a bit overdone, kind of like alot of those guys who wear suits to a bar.
on the flip side, if you are just gettig off work and are in a suit, why not go to the bar. You don't need to change into shorts to look like every other slob there.