Welcome!
Your son sounds similar to my DD. She is 26 months and a very fluent reader. She can read most level 1 and 2 books without help, although she does sometimes need to ask what a word says. She is also a great talker and outgoing... all this means that there is no hiding "how she is" when we are out in public. She reads signs at the store, readings numbers and prices, etc. I know "the look" very well. Fortunately, she is tall for her age so she looks a bit older than she really is. Even so, she can easily become a spectacle, as much as I try to be low profile.
As far as preschools and IQ testing -- I think a lot depends on the personality of your child. My DD seems to enjoy everyone, and she loves babies. She she doesn't care that none of her friends can talk in long sentences or read or engage at the level of imaginative play that she does. She seems to be very adaptable and does fine in any environment. I'm not worried about academics at this age, she soaks up plenty of stuff on her own. I just want her to have fun and make friends.
My DS, who is also highly gifted, is a totally different child. He had no interested in other kids (except for much older kids) and preferred the company of adults. We have yet to find a preschool that can really "handle" him has he is extremely self-directed and independent - which is a nice way of saying that he has trouble following rules. He's starting a gifted pre-K in the fall but we aren't sure how that is going to work out. (He's three, by the way, almost four.)
This message board is the only place I talk openly about my kids. I learned quickly that friends (and even a lot of family) didn't want to know that our 8 month old baby was counting to 10 forwards and backwards. Seriously. I even stopped blogging because as much as I tried to hid things, it was hard to share even simple family stories while totally hiding the fact that my kids are so different than most. It can be exhausting trying to "cover up" for them, and not a healthy practice anyway.
So, I can say that I've become much more isolated.
I don't know if you are open to letting your kid play on the computer, but my daughter really loves it. She navigates it on her own (we bought a small-sized mouse that is easy for her to use). She likes to play games on PBSkids.org. Your son may really enjoy it too - it'll feed his word/number addiction and give you some time to take a break!
Anyway, that was just my long winded welcome. I'm always thrilled to see parents of very advanced toddlers here.
