Hi Margaret, the thing to remember is that if people book this type of holiday, its because they want to meet other people and make friends.
I am going to Tuscany in 7 weeks time, it will be my 3rd JY holiday, I did the Austrian Lakes last May which was lovely, and I am also booked on a JY long haul holiday next year.
Go for it and enjoy, its a very social type of holiday, and you will be well looked after by your tour manager and in my experience you need never be alone unless you choose to be.
Ange