Is it safe to do this trip alone?

Yes, it is a well-trodden route. Stick to daytime travel and avoid arriving at the border or bus stations after dark.

Do I need to pay an exit fee leaving Mexico?

Yes, if you stayed longer than 7 days, the fee is approximately 700 MXN. Keep your receipt if you paid it at the airport when you arrived.

Crossing the Border from the Yucatan to Guatemala by Land

Travel by land from the Yucatan to Guatemala by taking a bus from Chetumal to Belize City, then a second bus to the Melchor de Mencos border crossing. From there, take a local shuttle or taxi directly into Flores, Petén, the gateway to the Guatemalan jungle.

Book your ADO bus to Chetumal. Purchase a ticket from your origin in the Yucatan (Cancun, Tulum, or Playa del Carmen) to Chetumal. Aim for an early morning departure so you arrive at the border before 2:00 PM.
Cross from Chetumal to Belize. Take a taxi from the Chetumal bus station to the Subteniente López border crossing. Walk across, pay your Mexican exit fee (approx. $35 USD if not included in your flight), and get your passport stamped.
Navigate Belize to the Guatemalan border. Take a bus or shared shuttle from the Belize side of the border to the Western Border crossing at Benque Viejo del Carmen. This is the official transit point into Melchor de Mencos, Guatemala.
Clear Guatemalan Immigration. Walk across the border bridge. Present your passport for an entry stamp. There is no official entry fee for most nationalities, but expect to pay a small 'processing' tip to local agents if you want to avoid delays.
Secure transport to Flores. Once in Melchor de Mencos, shared minivans (colectivos) wait outside the immigration office. They cost about $10 USD for the 2-hour drive to Flores. Avoid private taxi offers that exceed $40 USD.

Is it safe to do this trip alone?: Yes, it is a well-trodden route. Stick to daytime travel and avoid arriving at the border or bus stations after dark.
Do I need to pay an exit fee leaving Mexico?: Yes, if you stayed longer than 7 days, the fee is approximately 700 MXN. Keep your receipt if you paid it at the airport when you arrived.