Even before going on T, everyone read me as male with my binder and hair short. I wasn't even on Testosterone when using the male bathroom first. However, I really think you'll be ok in one, Nygeel. Try it out at a movie theater, or mall, etc first so that you can get a feel for whether or not you pass in there. Most of the time, if you act confident enough, not scared and as if you really do belong in there, then no one will question you. I have seen a lot of feminine or andro looking guys while using the mens bathroom and I live in a small town in TN, where the stereotypical guy is a redneck or a beefy mofo with tats.
Remember most people don't even think about trans people, and even less of them when thinking of trans people think of FTMs.
Try to be careful using mens rooms at sports bars and pool halls though, because sometimes they can only have one stall - and sometimes that one stall does not have a door separating you from others and all the cover you have is a wall dividing the toilet from the urinals.
I wouldn't suggest going in with a lot of friends. It looks weird. None of my guy friends go into the restroom with me. In fact, if we're all drinking and some of us have to use the restroom, we either wait til the other gets back or go a couple seconds later. I have never went into a bathroom with another guy before, because I think that actually puts you more on the spot than going in along; it draws an incredible amount of attention.
If you go in with confidence, don't really make eye contact, then I assure you that you'll do fine. Just like I said, try a theater restroom first or at a family mall. Somewhere friendly. Bars and clubs should be tried after you feel comfortable.