Meaning exactly what it says, you better hope.
I originally heard it in Florida, Tampa bay area. Most people use the term improperly. Look @ Examples.
Improper:
Guy 1: You're so gay.
Guy 2: You better hope.
Proper:
Guy 1: I got the money I owe you.
Guy 2: You better hope.
Proper+Akward:
Guy 1: Good thing you like women, because us two guys hang out quite a lot.
Guy 2: You better hope I like women.