The sale of single family houses in San Diego County in May shot up 21.5 percent to 3,750, compared to the prior year’s May sales, following a relatively strong sales month in April, according to a June 13 report from Dataquick.

Except for Riverside, five of the six counties in Southern California showed double digit sales increases led by Ventura with a 43 percent hike in sales.

“The market is being slowly nursed back to health by low interest rates, a modestly improved economy and, we suspect, a widening sense that the housing sector is at or near bottom,” said John Walsh, Dataquick’s president.

The median price for the houses sold in San Diego for May was $335,000, up 3.2 percent from May 2011. The overall median for all houses in SoCal was $295,000, up 5.4 percent from May 2011, the report stated.

The regional median price was the highest it’s been since September 2010 when it was $295,500.

Another sign that things may be loosening up: 22.4 percent of the sales regionally were for houses above $500,000. That’s the highest that segment has been since July 2010, Dataquick said.

However, distressed sales, including both foreclosed and short sales, made up nearly 45 percent of the resale market, the report said.

Thanks to historically low interest rates, the difference between owning and renting was also moving in favor of buying with a typical monthly mortgage for the entire region at $1,100, down from $1,154 in May 2011. The median rent for a two-bedroom apartment in San Diego is about $1,300.