Legality of "public space" Please help me out thanks!?

I'm curious about the legality of a "public space." If there is a hotel with a waiting area considered "public" (sign states as such, Open to the Public from _____ to _____). If you are within that public space during the given times, what are your rights? Is the hotel allowed to kick those considered "unwanted" out? Couldn't they discriminate based on cl, ethnicity, etc? Seems to be a grey area, trying to help out a friend for debate. Examples of cases would be even better. Thanks a ton!