San Francisco, California - If a Mexico beach vacation is on your radar, the best time to go if you want to get a deal is late summer or early fall. That's according to the travel experts at Expedia, who have combed through its treasure trove of vacation booking data to determine trends and offer helpful, money-saving advice.

Our southern neighbor has always been a prime leisure destination, not only due to its proximity but also because it generally costs a lot less (and takes much less time to get there) than a transatlantic or transpacific trip. And of course the country's beaches are hard to beat, lined with a variety of accommodations ranging from charming boutique hotels and convenient all-inclusive properties to big, busy and action-packed mega-resorts.

While Mexico is almost always a bargain from the U.S., the best month to save money on a Mexico vacation is September, when airfares from the U.S. tend to bottom out, according to Expedia data. The company notes that a Mexico vacation can be even more economical if you book your airfare in a package with your hotel – something Expedia specializes in.

"Booking a flight + hotel bundle with Expedia could save you up to $600 on your trip," the company said. You can also pre-book various tours and activities through the site. (Note: Every Monday, Expedia posts its 'Most Loved Destinations' deals for hotels and airfare/hotel packages with savings of 20 percent or more – bargain hunters can check them out HERE.)

In any case, Expedia's booking experts advise that travelers hoping to snag the best prices on a Mexico vacation at any time of year should: 1) Plan to depart the U.S. on a Thursday or Friday, 2) Search and book hotel rooms on a Friday night, and 3) Search and book flights on a weekend – especially Sunday – at least three weeks in advance.

Of course, summer at Mexico's beaches can be hot and sometimes rainy. But average temperatures run in the high 80s in summer months, compared to the mid-to-low 80s in springtime. Summertime rain typically blows in for a few hours in the afternoon - perfect time for a siesta!

With those tips in mind, there's a list of Mexican beach destinations that Expedia says are trending for trips this summer, along with suggestions on when to travel, where to stay and what to do on SFGate.com.