>For instance, I once pronounced "exit" as "eksit", and a guy from Ohio understood "axe it". So I made sure I pronounced it as "egzit" henceforth - and then in Pennsylvania I heard "eksit". So it seems most of the rules are local.

Yep.

Personally I feel that Americans are a little more tolerant of accents than a lot of other people. Of course, it may be that Texans are, or at least Houstonians are, because after all, so few people living here were actually BORN here.

One of the most amazing things I remember about basic training in the Army (besides being scared out of my wits) is the variety of accents from the various parts of the country. Arizona, California, Pennsilvania, North Dakota, Texas, Georgia...and nobody could understand the guy from New York City.

There is one key element to understanding proper Texan, however, and that is understanding the inflections of the word "y'all". Many parts of the country outside of Texas use the word improperly, referencing the singular instead of the plural. In reality, there are four proper usages of "y'all":

1) "y'all" refering to a group of people. Example: "Y'all wanna go to th' dance tonite?"
2) "alla y'all", when addressing all of the people in the group. Example: "Alla y'all cain't fit in th' back of mah pickup."
3) "suma y'all", when addressing only a portion of the group. Example: "Suma y'all git in th' front of th' truck."
4) "nunna y'all", when excluding everyone in the group. Example: "Nunna y'all fall outa th' back while we're drivin."

I'd be willing to bet THAT is never covered in any English classrooms!