Sept. 24, 2020 UPDATE
Our US Consul in Merida has announced that the US Consulate is accepting our ballots, in fully-stamped, addressed envelopes between 8:30 AM – 4:30 PM of any work day.
Notice that the US Consulate now says we should get the ballots to them
~ BEFORE OCTOBER 1’st ~
https://www.facebook.com/ConsuladoEstadosUnidosMerida/videos/896529154208545/
plus she includes information for any US citizen on how to get a ballot for just their Federal Elections, to send back to their County clerk’s office.
Her instructions:
1. Register to Vote .. or Confirm your registration with your state.
Go to http://www.FVAP.gov to connect to your state’s website to vote.
2. Request your ballot from your County Clerk … Do this right away.
You may also complete a post-card application that allows you to request an absentee ballot for all federal elections for your voting district.
3. Receive and complete your ballot. States are required to send out ballots 45 days in advance of the election.
4. Return your completed, signed ballot. … You may be able to do this electronically, if permitted by your County Clerk’s office.
5. You can drop your ballot off at your US Consulate:
The US Consulate in Merida is accepting our ballots, in fully-stamped, addressed envelopes between 8:30 AM – 4:30 PM of any work day – in a drop box at the door of the Consulate.
Finally, Yucalandia recommends that you drop off your ballot at the US Consulate get the ballots to them ~ BEFORE OCTOBER 1’st ~ … to be delivered to your County Clerk’s office in time.
Read on, MacDuff ..
Surviving Yucatan 
Some words of caution, especially for absentee voters. Relying on your county board of election to ship anything by MAIL to you, is ill-advised. I suggest inquiring if they can provide an application to you by email, which worked for me. I registered by return email (NY) and was able to vote as a federal and state voter in the primary (as detailed at my blog, linked below). But to do so I sent my downloaded digital ballot by FedX to a friend in Florida, who had it hand cancelled at a US Post Office in Florida. My board of election confirmed that our ballots were received and counted.
Example:
Colorado offers to either fax your absentee ballot to you … or to email your absentee ballot to you.
Because Mexican main can take easily 6 weeks to 8 weeks to deliver a letter from the the USA, Eric’s advice to request your ballot be delivered by email or fax, makes good sense.
Thanks, Eric, … Steve
UPDATE. Today I put up a cautionary blogpost about the EXTREME RISKS of voting by mail. I urge all Americans to consider these shared observations.
I should also emphasize NEVER to send a ballot by a private carrier to a board of election. It will be invalidated. It must travel by US Mail, and should be HAND CANCELLED, to establish date of entry into the mail stream — as current postal practices are in serious doubt. (There is no guarantee that ballots handed off by diplomatic courier will be postmarked with a readable time signature, even if deposited at a consular office.) BE ALERT. BE THOROUGH. DEMOCRACY IS AT STAKE.
Check with your County Clerk … Quite a few of them have accepted UPS, Fed Ex & DHL deliveries of our absemtee ballots in the 2016 & 2018 elections.
For sure use the US Postal Service if your clerk requires that
… but for cases when using the State Department & USPS combination after about Oct 16’th means your ballot will very likely not be delivered before many State’s deadlines, then using DHL, Fed Ex, or UPS – as approved by your County Clerk – is your best bet.
Thanks, Steve. I should have said NEW YORKERS. Under Article One of the Constitution (Election Clause), elections are managed by the individual states.
Several years of pain-free absentee voting from Mexico to Alaska:
1. After receiving your emailed application for absentee ballot, Alaska sends you the ballot by email or fax, whichever you have requested.
2. Return the completed ballot by fax, which is the only choice.
3. Keep a copy of the print out which shows the fax was successfully sent.
4. A few days later call to verify that your ballot was received.