Most of my fedex packages track through Miami and then Guatemala before coming to Belize. It takes up to 24 hours for me to receive a package once it hits Belize.
As far as clearing goes, if you track it and have duty clearance prearranged it can be cleared within 24 hours most times.
I see that Mail Boxes Etc handles DHL. They automatically clear packages and call you when they are ready to be picked up in San Pedro. They have set fees and seem very efficient.
I have had many packages arrive at MBE and I wasnt expecting them so they were pleasant surprises.
They seem to clear packages once a week .
The post office has some type of express service, costs the same as fedex and dhl, but if the package is lost you cant track it til it is missing for over 30 day!
Thankfully I have never lost a package with Fedex or DHL although back a few years ago the DHL service provider on the island would hold itmes for ransom and threatened not to deliver them unless you paid a $10 delivery fee. That is no longer the case.