It is never bad to request a card. We all have to start our collection some
place and QSO parties are a good place to pick up new states.

An SASE is the appropriate for sure.

Most of the contest folks will answer, some won't of course. One thing that
can help is to jot a note saying something to the effect - "Thanks for my
first California contact" or "Thanks for my first XXXX county contact in
California". When they are the first contact for someone they seem to
respond more favorably, they usually realize it is special to you and you
have taken the time to send a card and SASE so it is worth their time to get
one back to you.

Good luck and happy card hunting. Remember, once you get card fever it can
become addictive.