depends where you're going most of all I guess...
it was my 29th on the Friday just gone, and I stipulated "suits if you can be bothered" just because I wanted to wear mine (as I haven't had a decent opportunity this year).
I felt very comfortable, and not at all out of place, at the first couple of places we went (cocktail bars - and several women approaching me to tell me how hot they thought I was didn't hurt), and then ended up at my local (dingy old man pub), which was fun for the novelty, and I was certainly too drunk by then to be self conscious about it.
by the end of the night (I can't recall this bit at all

), we had ended up in the local meat market club, I have no idea how well it was received there
TL;DR: if you want to wear a suit, wear a suit, your birthday is no time to be worrying about how others see you
