Grew up about 15 minutes south of Santa Rosa in Petaluma. Great small town back in the day. Santa Rosa grew fast (mall, chains, gangs, etc.)
Santa Rosa is located in a great spot (close enough to the Bay Area, northern California coastline, wine country, central valley, etc.)
Nightlife might be a bit restrictive for a young person these days, not sure what the club scene is like. Most of my friends that live near there are married w/kids so our activities are parties, sports, etc. There used to be a happening bar scene w/bands etc. downtown and in Petaluma (Petaluma still features an art and music culture.)
Shopping is wide open. There are all your major chains and several local businesses to cater to your needs. Prices are high but most certainly not as expensive as a major city or in Marin County to the south.
The landscape could be considered less congested and is a beautiful area (hills and oak trees or open flatland.) You can be travelling through farmland in 5 minutes. You can be on the coast in 45 minutes to an hour. You can be in wine country in 40 minutes. You can be in San Francisco in an hour and a half.
Traffic in the town is absolutely horrendous. The problem exists because of small roadways or inadequate access for present loads. The freeway through town is being widened which will help. All the alternate access roads, that us locals would use back in the day to circumvent the freeway, are now crowded.
The personality of people in the town might be considered laid back, hippyish, liberal, etc. it is northern California afterall. There are young professionals, middle age families, tons of hispanics, plenty of rural types too.
Real Estate market in the area went through huge growth in prices about 5 years ago. Seems to have leveled off or lowered in the last 2 years. Still is rather expensive to someone who like me, who grew up here. I am sure it is less expensive than almost anywhere south of Santa Rosa though.
Overall I would say a young person might find it sort of boring, but at my age I find northern California (live in Ujiah now) to be fine for me.
Oh yeah since this is a tech forum board I will mention that Santa Rosa has a CompUSA that is not closing. Has a best buy. Has an Office Depot. Has an Office Max. Has a local computer show at the fairgrounds. Your internet access is most likely going to be cable or dsl (Comcast Cable or Pacific Bell I think) in almost any area of the town you choose to reside.