awap:
If forcast holds and it passes Coz on thur/Fri and is north of Cuba on Sat, I'd expect your flight may get a bit bumpy and your diving will be uneffected. SCC may not be able to cash much in travellers checks. They will probably send you to the downtown bank where I recall the hours were a PITA. I stopped using travelers checks after my first couple trips. As I recall, they worked OK for the wife's shopping sprees as long as you didn't make any mistakes filling them out. I prefer cash and credit cards now.
Some Lessons and Helpful Tios re: using Travelers Checks in Cozumel:
As far as actually CASHING the travelers checks for you, don't expect Scuba Club to do it without a commission, although I'm sure they are happy to take them as payment if you haven't already pre-paid.
You DO NOT have to go stand in line at a bank to cash travelers checks...in fact, avoid the banks at all costs because you will stand in line forever! There are change houses all over the place and the rate is no better in a bank when you consider the time you spend standing in line and the commission the bank will charge you.
The KEY to using travelers checks here (or anywhere for that matter) is to make sure you sign them in the correct place and using the same signature as you originally signed them with.
For example, I had a very good customer, who I KNEW and could of course vouch for, but she signed her counter signature with her initials rather than with her full signature as she did when she signed them at the time of purchase. There was not a bank or change house in town that would accept them...the signature was completely different obviously. I had to take her to the American Express office where she had to countersign all of them again on the back, with her passort information and US address. It was a royal PITA.
Another mistake people often make when using travelers checks is they make them out to themselves! Those checks become worthless to the merchant when you do that. The only option at that point is to take them back to your bank when you get home and deposit them in your account.
It is always best to leave the "pay to" field BLANK and let the merchant fill it in (most of us have stamps). Here in Mexico, we have corporate/legal names and then we have commercial names so for example, if you made your checks out to Blue XT~Sea Diving...I cannot do anything with them...because that is not the bank account name. Blue XT~Sea is the commercial name, not the legal name.
When I send out my payment options, I send all of this information to try to head off any problems...although sometimes people still don't read all of the information they are sent
It also helps (and is often required when cashing them) to have your passport with you when using travelers checks.
Don't expect your change back in USD, most likely if you have change coming back to you, it will be in pesos at whatever that establishments exchange rate is.
So what is my point here? If your travelers check is rejected, please don't get angry or frustrated with the merchant or change house. Remember, the whole point of travelers checks is to provide a very secure method of payment to the merchant and to the consumer in the event of theft or loss. With that in mind, the banks/merchants have to be very careful (here or anywhere) when accepting them, and if the signatures do not match or if they are made out to the wrong person...they cannot be accepted.
Using travelers checks doesn't have to be a PITA if you remember these easy "rules."
Have fun!