Unsure about local groups in the Vegas area, which is surprising to me considering the great weather and interesting areas to ride. You might need to start nosing around locally to see if there is a group already there.
Vespa Club of America is a nationwide club. Membership is $35/year. you get discounts at numerous retailers, roadside assistance with 25 mile tow (which can be extended to 100 miles), monthly newsletter, and some decals and a patch. The roadside assistance plan is worth the $35 if you don't already have a plan or replace your existing one.
https://www.vespaclubofamerica.com/