Delta has put many routes between the US and Mexico on "sale" right now. I say "sale" because Delta doesn't have a published award chart anymore, but we know from charts maintained by people like us online that the standard lowest level US > Mexico award price is 17,500 Delta miles one way. Right now many routes are only 12,000 SkyMiles roundtrip.

Through July 12, 2017 (tomorrow) at 11:59 PM ET, you can book roundtrips within the United States (on select routes) for travel September 6 through October 31, 2017 for only 20,000 Delta miles.
Sale Routes
Delta states that the sale applies to award flights with the following origins/destinations:

Washington, DC
Jackson, WY
Bozeman, MT
Idaho Falls, ID
Reno, NV
Phoenix, AZ
Knoxville, TN
Philadelphia, PA
Boston, MA
Salt Lake City, UT
Rapid City, SD
Las Vegas, NV
St. Louis, MS
San Antonio, TX
Buffalo, NY
Sacramento, CA

Flights don't need to be direct.

In light of the fact that the Delta co-branded American Express cards (both Gold and Platinum) have enhanced sign up offers ending soon (on July 5), a little over a week ago you saw me dive into the reasons why I think SkyMiles are worth collecting.

One of the points I mentioned was for redemption on market standard/cheap economy awards.

Each day we edge closer to the end of the year, which is significant if earning elite status is on your radar. You've got just under two months to meet elite qualifying requirements if you want status in 2017.

And the American Express Delta credit cards have limited time, enhanced sign up offers that end day after tomorrow--November 9.

Through December 31, 2016, you can earn double the rewards on purchases that normally fall into the non-bonused category of spend when you use your Amex card at eligible small businesses. The only stipulation is that you register your card first.

In light of the news that American Airlines is changing to a revenue-based award earning structure, and the fact that all three major US carriers now abide by a revenue-based award earning structure, I am writing a series of posts about when and where you should diversify the award miles you earn through paying for airfare.

For travel in July through Mid November 2016, Delta is discounting Economy awards between Atlanta and Brazil.

As far as I can tell, it only applies to travel specifically between Atlanta and Rio de Janeiro or Atlanta and São Paulo, no other North or South American cities.

American Airlines, United, and Delta all release several co-branded credit cards with various benefits, bonuses, and fees.

I have attempted to summarize the following cards on one table for easy comparison:

Some credit card offers in this post have expired, but they might come back.

Aerolineas Argentinas resumed flights from Miami to Cordoba, Argentina on July 5, 2015, 16 years after the last flight on the route.

Alitalia Business Class award space is wide open in Spring 2016 from New York and Boston to Rome for 62,500 Delta miles each way. Many days have three award seats in nearly flat beds.