I agree with
icewolf08 100%
I've been into photography heavily since grade school and I can say with all honesty, taking photographs in a theatre is one of the most difficult things I have ever had to do. Most cheap camera's do not like to take pictures in low light conditions and you really need a camera with Manual controls which you can personally adjust then a full auto camera with limited features. I agree with the above post, I am myself a Nikon user and do not know much about the Canon DSLR's but I can vouch that the Nikon D40 or D40x are great cameras. Two of my friends have them one has a D40x and the other has a D40 and they both love them. You can find them for cheap now as the newer D60 is now taking their place in the low end of Nikon's DSLR range. Try and save an extra $100 or so and grab a D40.
If you really can't afford a Nikon D40 then icewolf's suggestion of a Canon Powershot G10 is also adequate as it is an advanced point and shoot camera which does have the option for mostly manual control.
The great news is the D40 with the 18mm to 55mm zoom lens is on sale right now at B&H Photo/Video new for $450 and used for $350 check it out! If I didn't already have the Nikon D80 I would go for that!
http://www.bhphotovideo.com/c/used/4...al_Camera.html
I was in the same situation about 2 years ago. However I personally went with the Nikon D80 (Which is now being replaced by the D90
) and I haven't looked back since! I love my D80 and it takes wonderful low light pictures. Try and find some photography classes, they will help you learn how to use the manual controls on your camera to get the best pictures you can!