For a college student looking to cut loose on spring break, nothing says "mas cerveza, por favor" like a cheap trip to Mexico.

But a new report warns students to do their homework before taking the bait on one of those promised trips on the cheap, because the fine print can contain hidden fees that can jack up the advertised price by 30 percent or more.

A one-week trip to Acapulco advertised at $499, for instance, could end up costing anywhere from $598 to as much as $1,016 once additional fees are factored in, says a report released last week by the state Public Interest Research Groups.

"An entire industry now exists to provide college students with their ideal spring break," said the report, titled "Spring Broke."

"Unfortunately, the industry has adopted a set of deceptive marketing practices that make their trips appear less expensive than they really are," it says.

Advertisements for inexpensive jaunts to Mexico or Florida are ubiquitous on college campuses, but the fliers proliferate in February and March with the approach of spring break, the one-week vacation, typically in mid-March, that helps students ease into their impending final exams. Travel to exotic locales has become an annual spring break ritual for thousands of students.

According to the PIRG report, more than 500,000 college students will head to Florida this year for spring break, and at least 300,000 more will travel outside the United States to places such as Mexico and the Bahamas.

Many of those students will accept travel packages they find in advertisements plastered on billboards all over campus. Such packages advertise one price for the entire vacation, including arrangements for airfare and hotel accommodations.

The authors of the CalPIRG report asked students at 12 different colleges and universities throughout the United States -- including University of California campuses at Berkeley, Davis and Santa Barbara -- to scour their campuses for leaflets and fliers advertising spring break trips. The authors used the surveys to identify 17 travel companies that advertise on campuses, then searched company Web sites and called customer service hot lines to determine fees.

The group looked at prices for a one-week trip to Acapulco departing in mid-March. Prices are based on the per-person price for a four-person hotel room.

Researchers reported hidden fees averaging $367 for such extras as departure taxes, processing fees, peak week surcharges, late booking fees, departure city surcharges, cancellation charges and travel insurance.

Merriah Fairchild, CalPIRG's higher education advocate, said students should research the deals to avoid getting "fleeced."

"We urge students not to get distracted by the teaser price you see on a poster or flier," Fairchild said. "Be sure to find out about all of the hidden fees that come with each package, and shop around for the best deal."

Some of the travel companies singled out in the report took issue with the findings.

"I would like to know where the advertised $499 price came from," Matthew Scriven, who works with sales and marketing for Paradise Parties, wrote in an e-mail exchange with Scripps Howard News Service. "We do very limited print advertising, and (I) do not recall any Acapulco advertisements. Most of our advertising is done on the Web and only directs students to our site with no prices stated in the ad. Students can get an exact price on our Web site."

The CalPIRG survey said Paradise Parties adds fees of $517 onto the trip's $499 price tag, for a total cost to students of $1,016.

A customer service representative with Student One Travel -- which the report says adds $365 in fees onto its $619 Acapulco package -- said none of the fees are "hidden" from consumers. The representative, who declined to give her name, said the company does occasionally add extra fees, such as a peak week fee during busy travel times, but she said all those charges are clearly explained in company brochures. Students know the exact price of their trip prior to booking, she said.

Julia Cato, campaign coordinator for Spring Broke at UC Berkeley and a third-year communications major, said she was surprised to learn how much the additional fees added up to.

"Students are not completely gullible," Cato said. "They anticipate some sort of markup or hidden fees, but some of them were double the price of the trip."

Cato said some of the advertising of "all-inclusive" spring break getaways are misleading. Cato said a spring break trip to Cancun, Mexico, last year ended up costing her between $200 and $300 more than she expected to pay.

She hopes the report will inspire students to do their research.

"You're in college, it's really stressful, and so you make these plans to get away on spring break, and a lot of people overlook the fine print because they figure they don't have time," Cato said. "But it's important that you do take a look at it."

Patrick Tierney, professor of commercial recreation, parks and tourism at San Francisco State University, said college students tend to be inexperienced and, in some cases, naive travelers who often fall for the lure of a cheap trip.

"There's all these little, fine details that are usually in very small writing and some of them (students) are not investigating very well or not knowing what to look for, and they get sucked into either saving very little or paying more than they need to pay," Tierney said.