They cn file for a divorce in the state where they presently reside.
yes
no
No, being married outside of the U.S. will not create a problem in obtaining a divorce.
I don't think so.
They may obtain a divorce while living in the US, but since they are not US citizens they will need to contact the British Embassy/Consulate to obtain information on the correct procedure.
My husband & I (non-US citizens) were married while travelling in the US. We were married in Lake Tahoe, Nevada and it is a legal marriage. This may vary from state to state...Nevada has pretty relaxed marriage laws. If a marriage is deemed legal under the laws of one state, then it will be recognized as legal in all other states.
Tens of thousands
Unless you've got the Mexican citizenship, no. Also, I think divorces in Mexico are more complicated so even if you have the Mexican citizenship I think it would last more than just 4 days. I recommend Las Vegas :)
No. Marrying in a different country doesn't affect citizenship.
If you are both United States citizens it is not illegal, wherever you are married.
No the cayman islands are not part of the united states. You have to get a divorce in the U.S. or Puerto Rico.