I live in San Jose CA. I would pick the cheapest carpet and pading.
Well that all depends on your square footage and how BIG each room is (sometimes with small rooms you can get two rooms out of one piece also if there are hallways and stairs you can save money that way by using the scraps (long edge pieces) for those areas... If you are lucky, you may be able to get decent carpet and pad for 10-15 per sq yard... of course that doesn't include installation. The best place to go is to a wholesaler (most all are open to the public) they usually have installers or at least can refer you to installers who will do the job for a reasonable price and sometimes even the wholesale places will arrange it as part of the price (costs a little more but worth it). We carpeted most of our house right before we moved in... was about 800-1000 square feet and it cost us 1300 *roughly* including everything...
Carpets can range from 1 to 15 dollars per square foot depending on how luxurious they are. A middle ranged carpet would be for around 5 bucks a square foot.
Carpeting is measured by the yard. Measure the area you want carpeted and take it to a carpet store and get price list for the cheapest carpet.
