How far in advance do you need to get tickets for this tour, days? weeks?, thanks

That depends on what time of year you're going (summer is busiest), how many tickets you'll need, and what time of day you want to go.

If you've got flexibility in your schedule, and it's just one or two of you, then a few days in advance would probably be sufficient. But if date and time are important, you'll want to book your tickets at least a few weeks in advance:
http://www.blueandgoldfleet.com/html..._schedule.html

Also if you want them to mail them to you then leave time for snail mail!

Don't risk it - ALWAYS get your tickets in advance. As far in advance as you are comfortable with. I'd aim for three weeks minimum.

I've heard from too many people how disappointed they were that they couldn't visit "The Rock" on their visit.

Others have had to opt for the expensive City tours that take you all over the place - when all they really wanted to do was see Alcatraz - not Sausalito or Muir Redwoods, etc.

I would say as early as possible. We ordered ours 1 month in advance and had them sent to us. We were able to skip the pickup line.
Enjoy! Make sure to get the audio tour of the cellblock.