IT depends on the person. personally i dont think its rude not at all. just gotta make sure they are not wearing a RING on that finger.
depends if your looking for a date ya but if you just wanna hang no not really As long as they're showing you attention, go for it. On hint...If they say "OH, well let me get your number instead" Don't hold your breathe for a call. Keep your chin up and just chill.