Where should first time blackjack players play in Las Vegas?

Where you feel comfortable at. Most casinos are very willing to teach a new player the basics of the game. The dealer cannot tell you how to play your hand but, they can give you pointers. Also be aware of what the table minimum bet is, play according to your bankroll. Smaller casinos off the Strip are more willing to teach players, also plan to play when the tables are slow, if the tables are full it is less likely that they'll be willing to work with you, the dealers are expected to deal an x number of hands per hour.