Welcome to the forum.
Dear Sir or Madam, [You appear to have been in contact already - if so, you must have a name. Use it.>> Dear Mr // Ms XXXXXX]
My name is Persio X and I am willing would like to apply for a job in your company over the following winter. I am a student from Argentina and I am going to the United States on a Work & Travel program sponsored by X. I will arrive at Vail on November 29th 2008 and I will be able to work up to March 13th 2009 according to the J1 VISA I will have.
As I have studied English for over fifteen years and French for six years, I would be very interested to work in a position where I can be directly in touch with the public and practice these languages, such as a translator. [I don't like how this sounds]
Otherwise, I would also be keen on working in a position related to food and beverages, such as a waiter or a bartender.
My resume is copied given below.
Thank you for considering my application. I look forward to hearing from you soon.
Since you do not indicate what kind of company this letter is intended for, it is difficult to judge whether saying first that you want to make use of languages and then to say you want to work as a waiter or bartender makes sense.
If the company is [for example] a hotel chain, then I would rephrase that bit as:
I am most interested in using my languages (English and French) as well as working in a position related to food and beverage service, particularly as a waiter or bartender.
As you give it, adding your resume in the way you indicate is fine.