I've only sailed at Riva, there is space to rig, launching is down a wide wooden slip which points into the thermal wind so you need to lauch whilst it is light. As Chris said they are busy, however if they don't have an event (and they don't every week) they will let us sail there, they were very welcoming to us for the week after next when they have no event. As to whether they would run racing for us I'm not sure. I can find out as I'm there the week after next.
Torbole may be the better bet, the wind isn't quite as feisty on the Eastern cliffs and apparently launching is easier than Riva. We are going to pop over there whilst the SB3 worlds are on so I could investigate - perhaps we could join a general regatta for a few days combined with some blasting. Torbole is right at the Northern end and does have a very windy patch by the town should you wish to test your Cherub - and getting to the Western cliffs is only a couple of minutes sail away.
We are sailing the Cherub at Riva the week after next, we intend to take some video so you can all get a taste of what it is like.