Travelling with Asthma

Hi all,

I have asthma, and it is not too severe, but unfortunatly stress is a big trigger for my asthma, and i stress out all the time.
I have an oppertunity to travel to mexico for free with my boyfriend and his family. This trip is very important to him, and me as well. But i am very nurvous because of the humid climate.
Has anyone travelled into humid areas such as mexico with asthma?

This is a big stress on my life, and before i got asthma ( a year ago) i loved travelling , expecially to hot and humid climates. Now i am scared to death of travelling out of Canada.
Especially Los Angeles, ( i love la, tons of my family lives there)
but i know because of the pollution it could be a big problem.

I am also Canadian, so i dont know the hospital systems in the united states and mexico.
If i had an asthma attack, what would happen? If i had to go to the hospital, would they evan treat me? and if i did, would i be leaving with a heafty hospital bill?

Im also wondering about about airplanes. Anyone out there travelled on a airplane, with asthma, and had a asthma attack? What could i do? Nothing i think. But any one that could put my fears to rest would be great. I know things can always happen, and i cant controll everything, but these are legitamite things to wonder i think. So i want to know as much info as possible.

Is it possible to get travellers health insurence for pre existing health problems???

Any help at all would be very very muchly appriciated.