My friends and I tried this in Vegas one time when we were all 19. We had created outfits, practiced what we'd say, and even went to separate tables. One friend who dressed as a "european" student made it for about a minute before they asked for ID. My asian friend dressed as a "businessman" and made it for a good 5 minutes. I went all out and dressed like some stern, russian looking guy with long hair and shades. I kept silent and acted like I knew what was doing (had no fuckin clue). In the end I think I played for 15 minutes, then a pitboss came by and made me show an ID.
All in all, you won't get in trouble but they see this all the time and know how to spot you.
Edit: OTOH no one will even question you if you play slots though as long as you don't look "suspicious"