I've read a lot of material about Amsterdam's gay life. What's to expect of it?? Are the people friendly?? Is it predominately men or women?? young or older?? Any advice would be helpful.

First, about 20% of Amsterdammers are gay (and many more bi), so you won't feel alone
Second, Amsterdam is a relatively small city, and you can walk almost everywhere. There are four main gay areas: 1. Warmoesstraat (close to Central Station/Red Light District) which has the leather scene. The leather scene is less "strict" here compared to other countries, and you can also go to these bars in jeans/Tshirt.
2. Rembrandtplein area, mostly middle-aged and older guys, very casual and informal "gezellig" (cosy) atmosphere, lots of singing-along in pubs. Try Amstel Taveerne. In this area, Montmartre is a small dance bar that attracts a younger crowd.
3. Reguliersdwarsstraat. For the young and handsome, but some older guys go there as well. At this moment, SoHo is the most popular bar (check it out, it is nice), but April is also nice. Exit is the disco in this street.
Downtown is the name of a daytime place that is nice for coffee/lunch.
4. Kerkstraat, a mix of everything, not so popular. However, this area has the Thermos Day and Thermos Night saunas which are VERY popular.
Many bars have darkrooms, if you are into that kind of thing. Beware of pickpockets and play safe!
I would recommend the Orfeo Hotel. It is near Leidseplein, quite central and my friends tell me it has a nice atmosphere and it is easy to talk to other guests at the bar and during breakfast. About 2 stars, I would say.
Check out: www.gayamsterdam.com or www.simplyamsterdam.nl (gay section)
for more general info, try www.boomchicago.nl
All is predominantly for men, there are a few bars that cater to women, the most popular one is Vivelavie at the NE corner of Rembrandtplein.

Have a nice time here and if you want more info, please let me know.

Thank you so much for all your help

Sjoerd,
You say that 20% of Amsterdammers are gay and "many more" bi? So about 50% of the population of Amsterdam is gay or bi? That's a bit hard to believe.

I think this is a question of semantics, Magnus. By "many more are bi", I think Sjoerd means that in addition to the 20 % of the population that is gay, there are also a lot of people who are bi. I don't think he necessarily meant a "higher percentage", but rather that "in addtion there are also. . . "
On the other hand, I wouldn't be the least bit surprised to learn that half the adult population of Amsterdam has had at least had one gay or bi experience!!!