Corozal is not that big of a town, but you should be aware of Skeleton Town, which is where all the local trouble (like stabbings) take place. The Northern Highway runs through the west side of town. Skeleton Town runs along the east side of that Northern Highway, from about two blocks north of the bus station (don't worry, the bus stop is safe) and runs about 8 blocks north from that point. (I'd give you streets if I could, but no one uses street names in Corozal.) If you are in an area with NO STORES, be really careful. Daytime, Skeleton Town should probably only be walked with another person, and at night it should DEFINITELY be avoided all together. Otherwise, we have found Corozal to be quite friendly, and quite safe.
Take care with walking around the busstation at night. There are a lot of not-so-nice-looking people around there begging for money or trying to sell you things. But they are very polite though... Everyone welcomed me to Belize before they started begging for money or smoke... :)