My husband and i just returned from mexico, and both have what seems to be travelers' diarrhea plus additional symptoms (chills, dizziness, fever)?

Antibiotics: It is ideal that you get stool samples sent to the lab to determine the causative organism. If the cause is bacterial, you may need antibiotics such as Ciprofloxacin to treat the gastroenteritis. Please visit your doctor.

Stool samples : And examination are needed. May be an infection some of which are treated with antibiotics eg giardia some of which are not but if severe symptoms may require intravenous fluids etc

Travelers diarrhea: Sounds like you got it. It will likely pass. (Dr humor). Should clear on its own. In future recommend taking Bismuth subsalicylate tablets 2 qid if not pregnant. Read Jane Brody NY Times health editor on prevention and CDC has advisories.