With home prices still relatively low and mortgage rates trolling near their all-time best levels, it’s no surprise that home affordability is extraordinarily high in San Francisco and most U.S. markets.

According to the quarterly Home Opportunity Index as published by the National Association of Home Builders, more than 72 percent of all new and existing homes sold between January-March 2010 were affordable to families earning the national median income.

It’s the second highest reading in the survey’s history.

Of course, on a city-by-city basis, home affordability varies. 

In the first quarter of 2010, for example, 98.7% of homes sold in Bay City, Michigan were affordable for families earning the area’s median income and in Indianapolis, the percentage was almost 95 percent.

Indianapolis has held the top quarterly ranking for close to 5 years now.

On the opposite end of the spectrum, the New York-White Plains, NY-Wayne, NJ region earned the “least affordable” metropolitan area for the 8th consecutive quarter.  Just 20.9% of homes are affordable to families earning the local median income.

The rankings for all 225 metro areas are available on the NAHB website but regardless of where your town ranks, home affordability remains high as compared to historical values but it likely won’t last long.  Home values are recovering in many markets and mortgage rates won’t stay this low forever.

All things equal, buying a home may never come this cheap again. If you were planning to buy later this year, consider moving up your timeframe.

CNNMoney.com recently published its 2010 forecast and projections for home prices in the country’s largest metro markets. 

Listed as “Top 25″ and also comprehensively by state, CNNMoney.com’s home price forecasts puts Santa Rosa, California at the top of 2010’s home appreciation list and Hanford, California at its bottom.

The 10 cities projected for highest home appreciation in 2010 are:

1. Santa Rosa, CA : +6.0%
2. Cheyenne, WY : +4.7%
3. Kennewick, WA : +4.6%
4. Merced, CA : +4.4%
5. Bremerton, WA : +4.2%
6. Fairbanks, AK : +4.2%
7. Corvallis, OR : +4.1%
8. Tacoma, WA : +3.9%
9. Anchorage, AK : +3.8%
10. Bend, OR : +3.3%

The Pacific Northwest is the region most heavily-represented among price gainers. The Southeast and Middle Atlantic are most represented on the under-perform list.

However, just because a city’s homes are expected to appreciate (or depreciate) in 2010, that doesn’t mean that every home within its limits will follow suit.  Real estate cannot be grouped on a city level like CNNMoney.com tries to. There will always be areas in demand within city limits in which prices rise, just as there will be out-of-demand areas in which prices fall.

Real estate data can’t be grouped by city or even by ZIP code, really.

Real estate in Los Angeles is more local than that.

When we say “real estate is local”,  it means that every street in every town has a distinct set of traits that drives its home values. Homes that are one block closer to the train; or, homes that are facing north; or, homes that are made of brick. Each of these characteristics can affect a home’s desirability which, in turn, can affects its sales price.

National surveys can’t capture “essence” like this. They only report on the aggregate.

For local real estate data, look to established, publicly available websites and to active, local real estate agents.  Both will have data and insight that can help you.  National surveys often make for good headlines, but do little to help homebuyers find good value.

As the housing market improves across the country, certain cities are emerging as relative bargains.  Some areas, like Miami, were hit hard by the recession, and other areas are buoyed by good school systems and strong labor markets.

In this 5-minute video from The Today Show, 10 cities are highlighted for their home prices.  And they’re not “small towns”, either. 

Among the featured cities:

• Miami, Florida
• Akron, Ohio
• Tuscon, Arizona
• Minneapolis, Minnesota
• Trenton, New Jersey

Now, this piece is about finding gems on a national scale.  They exist locally here in Los Angeles , too.  You just need to know what to look for.

With mortgage rates low and tax credits available, it’s not likely that bargains will last.