"Crowd" is the noun for referring to just the group itself. "Crowded" is the adjective for referring to the situation of there being many people in the same place. So it should be "it's so crowded in here". "Can we please go TO another place?" --> by adding "to", it is now grammatically correct. "Can we please go somewhere else?" --> this is a perfect sentence and actually sounds way more natural than the one above too. I would also like to say that using "please" towards the beginning or a phrase is a little old fashioned and can also sound a little passive aggressive if your intonation is not perfect. So "please" should always be used at the very end of a phrase, in order for it to sound more natural nowadays and give the intended politeness. --> "Can/Could we go somewhere else please?"

It would be better to say, “It’s so crowded in here. Could/Can we please go somewhere else?” The “could” makes it a little more polite. You could also say, “Could we go to another place?”