Of course, I'd be happy to help you plan your trip to Mexico City, Los Cabos, and Cancun. Here are some tips that might help you:

Best Time to Visit:
Typically, the best times to visit these areas of Mexico are during the dry season from December to April, when there is less chance of rain. For fewer crowds, consider going in spring or autumn.

Route and Accessibility:
Mexico City has an international airport with several carriers. From Mexico City, there are regular domestic flights to Los Cabos and Cancun. All cities are well-connected by highways if you prefer road travel.

Altitude and Acclimatization:
Mexico City is at an altitude of about 7,350 feet, so it might take a couple of days to get accustomed to the thinner air. Hydrate well and rest as needed. In contrast, Los Cabos and Cancun are at sea level.

Accommodation and Booking:
Ensure to prebook your accommodations. All places have ample options ranging from luxury resorts to budget hostels. Airbnb is also a good option if you want to experience local life.

Clothing and Essentials:
In Mexico City, the attire can be casual or semi-formal. Los Cabos and Cancun are beach destinations, so pack your swimwear, hats, and sunscreen. However, if you plan to visit churches or religious sites, dress modestly.

Health and Safety:
Ensure you're up-to-date with routine vaccines. Stick to bottled water and avoid street food if you're not accustomed to it.
Ensure your travel insurance covers you in Mexico. Beware of your surroundings, especially in crowded tourist places, as pickpocketing can occur.

Local Etiquette and Respect:
Mexicans generally greet each other with a handshake, hug, or sometimes a kiss on the cheek. Always respect local customs and traditions. Try to learn some basic Spanish phrases, as this can greatly enhance your experience.