I just took a job in Concord, which is the city right next to Clayton. Walnut Creek is somewhat exclusive and is a nice area. It's not all that fast though. IMO older people live in Walnut Creek
In the city the population was spread out with 17.6% under the age of 18, 5.2% from 18 to 24, 27.1% from 25 to 44, 24.8% from 45 to 64, and 25.3% who were 65 years of age or older. The median age was 45 years. For every 100 females there were 85.8 males. For every 100 females age 18 and over, there were 81.5 males.
If you like old chicks!!!!
In the city the population was spread out with 26.5% under the age of 18, 4.5% from 18 to 24, 28.5% from 25 to 44, 31.5% from 45 to 64, and 9.1% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 96.0 males. For every 100 females age 18 and over, there were 94.6 males.
The median income for a household in the city was $101,652, and the median income for a family was $107,448. Males had a median income of $77,535 versus $50,279 for females. The per capita income for the city was $42,048. About 1.2% of families and 2.6% of the population were below the poverty line, including 3.6% of those under age 18 and 1.9% of those age 65 or over.
Both from Wikipedia.
I've been to Walnut Creek, and Concord on several occasions and they just seem like any other suburb, except land isn't cheap out there. If you don't like quiet I don't think you're going to like Clayton much. I'd recommend (if you like cities) either Oakland or Berkeley. They have their reputations, but anyone who's lived in either place has said good things. Berkeley's just different! Why don't you just try them out for yourself?