I think it's great that you're weighing the possible impact of more adult behaviors with concrete physical changes like shaving.

From personal experience, I was that girl that had to shave my legs and under my arms way earlier than my peers. My mother basically waited until I was starting to get teased about it and getting self-conscious before bringing it up. While it cut down on teasing, I do remember times when these weirdly adult behaviors got in the way of normal kid stuff (a really awful shaving cut/razor burn incident that made me skip soccer practice because I couldn't even put my shin guards over it).

That said, my advice is to be really clear about
what associations you want to make with shaving. If the appearance of facial hair doesn't bother him or break school rules, don't push the issue. If he mentions it, teach him how to shave and acknowledge this as a habit that comes with his body's changes as he grows up. Be careful to avoid accidentally playing into fears that these changes make him weird/bad/totally grown up. And if you're worried about him linking this behavior with other adult behaviors (drinking, sex, work, emotional stoicism, whatever), you can help clarify that those are related to emotional readiness while shaving, using deodorant, etc. are all based on physical changes.

11 is fine. I was 11 when I got peach fuzz on my upper lip and my dad refused to show me how to shave. He said I was too young. My mom finally showed me, which is why I used a disposable Lady Bic until I was 13.

The biblio-therapy reference by Amy might be a good idea just in a general education sense and in bringing up the subject.

I would suggest finding a serendipitous moment to look at him face to face - one of those 'I'm really proud of you moments' - and then you can make the observation about noticing that he has the early fuzz of a developing young man and you look forward to teaching him someday how to shave (when he is older). Follow his lead - if the conversation goes nowhere (now), don't worry about it.

He is at that age where he will (already is?) intently aware of his own body and its appearance (middle school age is the time) and fitting in with his peers and the opposite sex. He will come to you when he feels the need to do something about it. You will have shown him the door is open by your comments.

When I asked my father about shaving my peach fuzz, he said "once you start, you will be doing this every day for the rest of your life, so it's up to you". I decided to leave it alone till it came in a bit thicker.
Personally, I would wait until he asks you, which means its starting to bother him.

Some peach fuzz is not as bad as an acne problem.

He's a kid, make it seem like shaving is fun.(it kind of is :p) Approach him about the subject with a smile and tell him it's not such a big deal, even if it is to you. Let him know if he's ever interested in learning how you'd be happy to teach him.

I would recommend teaching good hygiene early on. Especially thorough face washing.

You're right not to push it.
Have a disposable razor handy in his bathroom, but not laid out for him. When he's ready, IF he wants, he'll pick it up and try it.

I would think when the kid thinks his lip growth is too much, then he'll want to shave it. But he'll grow tired of it on his own schedule...and perhaps by then, it will be coming in more fully and look better.

You always hear that if you shave, it will grow back thicker. That could also just be mother nature proceding along with the hormones and you never notice cause you keep whacking away the evidence...until you stop, you don't notice.

If he wants to start shaving, high school is plenty early enough, though there are those few early bloomers who start maturing in elementary school and are hairy mothers in phys ed all through middle school and into high school.