'Czekam przed wejściem do kina' should be also correct
"Obok wejścia"? Can you just say "przy wejściu kina"?
I just added "obok wejścia". I don't think "przy wejściu kina" is ok, though. Google shows some results, but very few of them actually mean "entrance to the cinema".
Yes, "obok wejścia" makes sense, added. Although technically it's "next to".