Martha Galbreath Robles knew she wanted to downsize, but she waited for the real estate market to stabilize before trying to sell her longtime home.

She never expected that within three days of listing her 5,000 square-foot home on an acre in the Killian area of South Miami-Dade, she would get five cash offers for her full listing price of $979,000.

“My house sold so much faster than I thought it would,” said Robles, 64, who bought a newly built home 10 blocks away in February for $529,900.

Robles is living proof of the new boom in the South Florida real estate market, as prices and sales of homes and condos jump, amid a flurry of new construction.

Strong demand and dwindling supply are propelling the median sales price of Miami-Dade properties, with condominium prices rising 26.9 percent in February to $165,000 compared to a year earlier, and 6.5 percent compared to the previous month, according to figures released Thursday by the Miami Association of Realtors and the local Multiple Listing Service.

The median sales price of single-family homes in Miami-Dade rose 10.9 percent to $194,000 year-over-year and remained the same compared to the previous month.

“Things are just crazy right now,” said Debbie Preston, a broker associate with the A Team at Avatar Real Estate Services in South Miami, which listed Robles’ home. “If people are pricing homes fairly, they are getting sold. Our inventory is very low.”

As evidence, another home Preston listed last week — a three-bedroom, one-bath in South Miami, for $499,000 — already has a pending sale.

In February, 849 single-family homes sold in Miami-Dade, up 6.8 percent in a year, figures from the Miami Association of Realtors show. Sales of condominiums increased 6.3 percent to 1,226.

“The market is amazing,” said Natascha Tello, chairman of the Miami Association of Realtors. Inventory is generally less than six months across all price ranges throughout Miami-Dade, and as low as one month for homes priced under $200,000, she said.

Rafael Diaz knows firsthand how hard it is to find the right home. During a six-month search, he made offers on five properties in Coral Gables and Pinecrest, only to lose out to higher bidders, before finally getting a contract on a 2,400 square-foot home in South Miami with a pool and Jacuzzi, for $805,000. He hopes to close in May.

“In that price range the inventory is limited,” said Diaz, 38. “The good ones go pretty quickly.”

The trend is spreading statewide, as sales of single-family homes rose 10.3 percent in February, compared to a year ago, according to data from the Florida Realtors. Condominium sales were up 7 percent.

In Broward, sales of single-family homes rose 7 percent year-over-year to 969, down 6 percent since January, while the median price jumped 23.2 percent to $227,000 year-over-year, up 1.2 percent since January, according to the Greater Fort Lauderdale Realtors.

Sales of condos and townhouses in Broward increased 0.7 percent to 1,245 from February 2012 and up 5.1 percent from January, as the median sales price increased year-over-year by 17.3 percent to $88,000, down 7 percent from January.

Chuck Bonfiglio, broker owner of AAA Realty Group in Pembroke Pines, listed a townhome in Davie for $110,000, and got five offers in two weeks. It is now under contract for $123,000.