I recently purchased the 60mm f/2.8 macro and its pretty amazing. I shoot with a 60D so the 1.6X focal length works for me. It does not have IS so its a bit challenging without a tripod.

I would recommend renting a macro for the festival... see if love it and than purchase it. If you work with a local photo shop and rent a lens from them and let them know you may buy it, more often then not they will apply the rental cost to your purchase.

Good luck and have fun, flowers are beautiful subjects.

Bruce