Hi Jenny, if you are too late to book Alcatraz all is not lost! I did the Golden West tour in 2011 and did the SF Bay cruise. Although we did not actually visit Alcatraz we sailed near to it and the commentary told us lots about the prison, so although it wouldn't be quite the same as visiting it you could still learn a lot about it that way. Hope you manage to get tickets though!
Hi Nicki, the age range of JY tours varies from tour to tour - I was 40 when I did the Golden West and I was certainly one of the youngest. The age range in general is 20s - 80s, with most being 55-75. Sometimes I'm the youngest on a tour, most times I'm not; having said that, as others will quickly tell you, everyone mixes well together on a JY tour so once you make an effort to talk to others you will be just fine!
All the best,
Bob