Mexico Unlimited offers MetroPCS customers a cheaper way to text, call, and Websurf in Mexico

It works like this: a $5 per month per line surcharge on top of your plan’s base rate grants you unlimited mobile-to-mobile and landline voice, unlimited texting to the U.S., and data on Mexico’s “leading providers.” And many of those benefits carry over stateside: you can place landline calls to Mexico at no extra charge, plus text and call cell phones. “MetroPCS is busting down the border to deliver a great experience for data and calling to Mexico that the other prepaid guys can’t touch,” said CEO of T-Mobile John Legere in a press release.

Mexico Unlimited, it’s clear, is targeted at those who traverse the border frequently. And according to T-Mobile, that’s a large contingent of travelers — in 2014, 35 percent of all international calls and 70 percent of international trips taken by small and mid-sized businesses were to Mexico and Canada.

So how’s the new plan compare to the competition? Pretty favorably, actually. AT&T’s cheapest international GoPhone plan is $55 per month, leverages a one cent-per-minute charge for calls made to the U.S. from Canada or Mexico, and doesn’t include data (1GB is a $25 add-on). Verizon offers a prepaid option that includes unlimited texting to Mexico and Mexico, but not calling (that’s extra $10 a month). And Sprint’s $5 a month Mexico-Canada Plus plan omits data.

If Mexico Unlimited has a catch, it’s that data speeds in the southern part of the North American continent may be erratic. T-Mobile says it’s partnering with “leading providers” that offer 4G LTE, but only “everywhere [their] networks reach.” In simpler terms, you’ll most likely be fine if you stick to densely populated metros like Mexico City and Iztapalapa, but venture into the rural countryside and there’s no guarantee of consistent coverage.

T-Mobile’s also restricting Mexico Unlimited sign-ups to MetroPCS customers with “a $40 or higher base rate plan.” Those who qualify can add the new plan option online or in MetroPCs stores starting today, and folks who enroll on or before August 31 get free Mexico Unlimited service until 2016.