The “For Sale” signs are just starting to sprout, but already experts worry that this spring home-buying season will be even grimmer than the last.

Despite tentative signs of recovery in hard-hit areas like California and Florida, the broader housing market is far from reaching bottom, economists say. Across much of the nation, prices are likely to keep falling into 2010.

So this March-to-June season, when most homes are bought and sold, will be bad, perhaps the worst since the market began to spiral down in 2006.

Across the nation, 19 million houses and apartments — nearly one out of every seven — are vacant, the highest percentage since the 1960s. But only about six million of those homes are for sale or for rent. That means millions more could still flood onto the market, depressing prices further.