As long as your comfortable infiltrating groups, you'll be fine, sounds like you are. Yes, everyone goes out in groups there, but even if you aren't travelling solo, 1 or 2 other dues doesn't make a group, and Colombian people are ultra friendly so I think flying solo in Medellin is better than going with, say, a sub-par gringo wing. Sounds like you're a big dude, you'll stand out, be cool to everyone and girls might not approach but will give you signs they want you to, and guys will be friendly and bring you in for drinks. Note: throw in for drinks but don't look like a sucker.
As far as safety goes, you'll be fine. Take taxis at night unless it's a very short walk in a nice part of town.
As far as safety goes, you'll be fine. Take taxis at night unless it's a very short walk in a nice part of town.