I am going to a wedding in October in Mazatlan then going to meet some friends in Belize. I would like to bus it from Mazatlan to Belize and will have about 4 days to make the journey. Does anyone have any suggestions on what route to take? And about how long will it take? Thank you!

You do realize how far it is, right? Even 'as the crow flies' it's approx. 1225 miles, generally speaking. That's going to be a LOT of time sitting on a bus, with only 4 days to do the trip.
Are you sure you don't want to fly?

bus or better fly Mexico City Chetumal cross to Belize..

I did some Googling around because I was curious about your question.

The route most people said to take is Mazatlan to Mexico City (12 hrs). Then Mexico City on to Chetumal at the Mexico/Belize border. Then on to whatever your Belize destination is.

One person mentioned 28 hours driving time, so would be longer than that via bus routes.

There were a few comments about busses in Mexico being a lot nicer than the ones in Belize.

Seems like flying at least the Mazatlan/DF portion would be the way to go.

I do realize that it a really, really long way in only 4 days but I also figured the bus would be more scenic than flying. I think I will look into flying at least some of the way.

Suze - what does DF stand for?

oh sorry...
Distrito Federal (Federal District) = Mexico City

I'm not sure after 4 days on a bus across Mexico & Belize you'll care much about the scenery (only partly joking!). I'm all for a bus ride and traveling by bus if you have a month to see Mexico (for example) but that's a LONG way in a SHORT time.

Also compare costs. Sometimes flying may be not even be so much more expensive.