In reply to Kevster:
1) When we went two years ago as a group at the start of June the snow had literally just cleared - we were lucky. We were planning on going this year same time but it was just too snowy! We were Cortina both times, climbing Cinque Torre.
2) We camped in Cortina, which was good for walking but not great for lower-grade climbing. VF is also something to try whilst you are there.
I also went to Arco last year for a while which was very nice: Lots of rock and short walk ins but very polished! Arco you can guarentee there won't be snow in May.
3) We ended up doing a lot of driving because we were staying in Cortina and driving up to Cinque Torre every day or so, which was a pain, but other than that its great for groups!