Vaccines for Mexico are Hep A and Typhoid. Don't worry about the timing too much. There is a combined Hep A and Typhoid jab for the anti-needle brigade and is cheaper if you go to the travel clinics, if you do go to the docs, they may charge you. I'm an NHS pharmacy student and i've just had mine and it cost a few quid(no staff perks).
The timings of these jabs are basically to make sure you do not have a bad reaction. You're immunity should kick in very quick.
Side effects: The Hep A hurts like mad and your arm stings and goes numb for a while. There may be a mild/severe rash with the typhoid if you have them administered seperately.
Yuck. Hate needles. Malaria tabs can make you quite sick, and it depends on the areas you are visiting. But this is one where you'll have to weigh up the pros and cons first. Preventing bites is the better option for some people. If you go to a travel clinic, they may try to persuade you to have them. Ask your practice nurse or local pharmacist. They have the most up-to-date info.
Happy, safe, bug free holidays.