You save a huge amount of money by booking a train ticket in advance. Likely, you'll have to come down to NYC, and then you can take a train to Chicago and from there to California. It could very well be cheaper to fly.

Just realize that you're going to need a car if you really wants to explore California beyond the major cities. There's no public transportation to speak of outside of parts of LA and San Francisco.

The Lake Shore Limited has a Boston branch. It joins the New York branch in Albany. You make a stop in Buffalo about midnight and roll into Chicago in the morning, almost always before noon.
The California Zephyr (#5) leaves Chicago at 2:00PM. Ride to either Sacramento or Emeryville. Buying the ticket (coach at least 30 days in advance will save more than $149.
You can carry your own food on Amtrak to save a little. Breakfast is the meal I like to eat in the dining car.
There are many good food options in Chicago Union station for lunch if you don't want to venture out onto Jackson Boulevard.
Check and see if the 15 day USA Rail Pass will save you money compared with individual tickets. If you need a break between Chicago and California, Glenwood Springs is a great town with a so-so hostel (Not HI). Sacramento has my favorite HI Hostel.
I seem to be the resident "expert" on Amtrak which draws some criticism from time to time on Fodors. Ask your questions. For a solo trip you might save some money by driving a cheap car to California so that you could get around once there.

Search carefully. It is very likely that flying will not only be much faster but also considerably cheaper.

Quickest way on the train is the Lake Shore Limited to Chicago and the Zephyer to Emeryville in the Bay Area. flying is indeed faster and usually cheaper, but if you want to see anything it's from 30,000 feet up.
The Chicago to Emeryville route is one of the trains that seems to run on time more often than not.
From Chicago for about the same price you can also take the Empire Builder to either Portland, OR ot Seattle, WA; or the Southwest Chief into Los Angeles.

Or should I consider looking for cheap airfare in advance? Suggestions? Answers?

I would go with this option. Cheaper, faster.

Flying will be faster, no doubt. If you can find a flight to northern California for less than $218 buy it now.
I priced an Amtrak trip from Boston South station to Sacramento starting on Monday 9/30/13 in coach all the way. There will be about 4 hours layover in Chicago if your Lakeshore Limited runs on time. If you started your trip tomorrow, the coach fare for the same trip would be $398.
The fare to Glenwood Springs is the same ($218) in early October. The fare on the next California Zephyr from Glenwood Springs is $120 to Sacramento or EMY (Emeryville).
For comparison, Fuel cost for the 3014 miles from Boston to Sacramento would be about $300 if you can meet a 10 cent per mile criteria.
Sacramento or Martinez are good jumping off points to take a San Joaquin train down through the Central Valley as far as Bakersfield. From Bakersfield you have a variety of buses to different Southern CA locations including one that ends up in Las Vegas.

My father-in-law took the Zephyer from Chicago to Emeryville & then bus to San Francisco a few years ago. He said the scenery was boring as H--- until he got to the Rockies.

Stu Dudley

If you have never traveled by either rail or hiway across the US - IMO - you should do it if you have the chance, and the railroad leaves the driving to them.

And yes, it may be flat in parts - but that still makes you better appreciate the beautiful Rockies and when you finally make it out here to the "Golden" state.

Used to live in SF and loved it - but now down here in SD - and hope you don't forget to come down and check out the best weather in the continental US.

However - don't get your hopes up re: employment prospects unless you are really a tekkie.

And when you arrive - suggest you somehow find a car and drive down the Coast hiway to LA and then to here/San Diego.

Flights back from SoCal to SF are pretty cheap if you need to do that.

Carmel/Monterrey has a lot to see/do (Aquarium, Cannery Row, artist shops in Carmel, etc) and just south of there - the drive along Big Sur is stunning - and spending a couple of days/nights along the coast is marvelous, maybe one night at cute Cambria - near Hearst Castle/San Simeon.

Plenty of other posts in here on that.

Also - Lake Tahoe is very beautiful and you will probably be checking that out as well as Yosemite, etc.