Here are the schedules for Chetumal to Belize buses...

The Premier buses depart from the ADO terminal in Chetumal. The other Belizean buses depart from Nuevo Mercado (New Market). The ADO website is http://www.adogl.com.mx/

Here are the schedules for Chetumal to Belize buses...

The buses are used Bluebird school buses; most of them are not very comfortable, not air-conditioned, and are not well equipped to handle luggage, but they are cheap! There are a few air-conditioned buses that are used on some Express runs. Buses operate on Sundays and public holidays, but on a less frequent schedule.

There are two types of bus service in Belize: “Regular” buses stop for passengers anywhere along the route, and “Express” buses stop only at main towns. The final destination of a bus is displayed in the front window of the bus.

In Belize City, buses arrive at and depart from the Belize City bus terminal (commonly known by its former name, Novelo’s) located on West Collet Canal.  When boarding a bus at a terminal, just get on and find a seat. Put luggage in overhead racks or at the back of the bus. Always keep an eye on your luggage because passengers often use the rear emergency door as an entrance or exit. I like to keep my luggage within arms reach if possible. Once the bus gets going, a conductor will collect the fares. If you’re on the side of a road and you want an approaching bus to stop, wave an arm up and down; the bus will not stop if it’s an Express, it’s full or the driver doesn’t feel like stopping. After taking a seat, the conductor will collect the fare. Buses tend to be crowded so try to get to the terminal well before the departure time so that you get a seat.

All bus providers have been given permits to operate within assigned zones.

1. Northern Zone – Belize City to Corozal (135 km / 84 miles)

The bus companies authorized to operate on the highway in the Northern Zone are NTSL, Belize Bus Owners Cooperative (BBOC), Chell, Gilharry, Russell, Tillett, T-Line and Venus. Northbound buses depart from Belize City about every half hour beginning at 5:30 am; last departure at 7:30 pm. Southbound buses depart from Corozal about every half hour beginning at 3:45 am; last departure at 7:30 pm. Most are Regular buses, but there are a few Express buses throughout the day. There is also bus service to the rural areas, including Sarteneja.

A Regular bus from Belize City:

to Orange Walk (87 km / 54 miles) is about 1.5 hours & BZ$5.00, and,

to Corozal is about 2.5 hours & BZ$9.00.

The Express is a bit faster and 2 or 3 dollars more.

2. Western Zone – Belize City to Benque Viejo Del Carmen (130 km / 81 miles)

The bus companies authorized to operate on the highway in the Western Zone are NTSL, BBOC, D and E, Guerra’s Bus Service and Shaw Bus Service. Westbound buses depart from Belize City about every hour (sometimes on the half hour) beginning at 5am; last departure at 9 pm. There is also bus service to the rural areas.

A Regular bus from Belize City:

to Belize Zoo (29 miles) is about 45 minutes & BZ$4.00,

to Belmopan (50 miles) is about 1.5 hours & BZ$5.00,

to San Ignacio (73 miles) is about 2 hours & BZ$6.00, and,

to Benque is about BZ$8.00.

3. Southern Zone – Belize City to Dangriga (169 km / 105 miles) / Placencia (257 km / 160 miles) / Punta Gorda (338 km / 210 miles)

The bus companies authorized to operate on the highway in the Southern Zone are James Bus Line, G-Line Service and Usher Bus Line. Buses authorized to operate in the rural areas of the Southern Zone are Chen Bus Line, Yascal Bus Line, Smith Bus Line, Richie Bus Line, Martinez Bus Line, Williams Bus Line, Radiance Ritchie Bus Line, and Polanco Bus Line.

I haven’t got complete schedules for all the bus lines, but here is a site with the James Bus schedule:

https://www.hickatee.com/belize_bus_times.html

info from http://belizebus.wordpress.com/