We shot a short with a couple Canon XL2s in 24P advanced mode (2:3:3:2 pulldown). It was edited in a 24p timeline. Up to that point no problem.

But the thing is, this is going to be screened at a couple local festivals and they are asking either Betacam or MiniDV copies for that purpose. Both formats don't support 24p playback, so I'll have to add a pulldown to comply with the NTSC standard. But although 24p footage with a 3:2 pulldown looks fine on a NTSC monitor / TV, I'm not sure how it will look on a projection screen.

Because if it looks anything like a computer screen, the interlacing artifacts (combing effect) introduced by the pulldown will be very noticeable. It is pretty noticeable on a small computer screen, can't imagine it getting any better on a big screen. Or does a projector work like a regular NTSC TV (odd and even line scanning)?

I'm wondering what processing if any I should pass my 24p footage through in order to make it look good when projected. 2:3:3:2 pulldown? 3:2 pulldown? With/without de-interlacing? Just making sure before sending the master out for copies.

The interlacing isn't your problem:
Most projectors have pretty good built-in deinterlacers.

So you're saying I should just add a standard 3:2 pulldown and it will look fine when projected?