Hello Lee and welcome to you.
I have done 8 JY tours, what I would say is IT IS YOUR HOLIDAY!!!! even if you go with JY and a group you do NOT have to stay side by side 24/7 of course you can stay out (Lucky You) but just mention it to the tour leader or else when they do a head count they might panic your missing. You can always do your own thing so to speak, just keep the tour leader up to speed. If your happy to just do your own thing that is fine, it will seperate you from people so just take that in mind, you might feel isolated when with the main group as bonding takes time.
These are just my thoughts you of course must do what you want it is your money and holiday.
I Have been to Prague (on my own not with JY this was before I found JY) a wonderful city I must say fantastic photo oppertunity's etc. I done a really great walk around the town to do with the Jewish Quater and the holocaust a theme close to my heart. So I hope you get to see this vibrant city, and give JY a go. If I can help at all just ask. OK
Cindy