Mexican etiquette for a friend who recently passed away...

A very good Mexican friend of mine passed away in Ajijic about a week ago.  The family have now invited me to attend a meal at the house of the deceased person.

What can I expect?  How should I dress?  Is it a celebration of the person's life or a time for sadness and prayers?

Probably a bit of both. Dress rather nicely, but not formal style, and be sure to take something to contribute to the meal; perhaps a kilo of coffee, a cake, or such.

Turns out the family was just having a get-together before the 9th day, which will be the following day.  A mass will be held at the local church in the morning followed by a large crucifix being taken to the Panteon later in the afternoon.