There's being friendly and then there's outright flirting. I am friendly with everyone, girls, guys, what have you. I've dated men who are the same way and I actually prefer that. Like when we're out to eat and he jokes around with the waiter/waitress or is just generally at ease with people wherever we go. This to me is a big turn-on. But if he's not that way with the men around, just the women, I would assume it's full-on flirting, in which case I would examine his treatment of me and go from there. If he treats me respectfully and I am secure in the rel
ationship with him, I might choose to be okay with it. If while he's doing it, he is disrespecting me, it's a kick to the curb ASAP. But that's me and you're you

.
You have to decide whether either scenario is something you can live with. In terms of your question, I'd say give him as much consideration as you would give anyone else you're in the beginning stages of da
ting. Pay cautious attention so you could decide for yourself whether he's a fit for you. If you behave outside of your norm, how will you ever find out?
Just my two cents. Good luck!

ETA: TurtleDove posted some similar thoughts as I was typing. Her whole first paragraph resonates with me. It's exactly how I think of it.