Sounds like a wonderful trip plan! Portugal, with its diverse cities and beautiful landscapes, is bound to provide you an amazing travel experience. Here are the tips to help you plan better.

Best Time to Visit:
The best time to visit Portugal generally spans from late spring (April-May) to early fall (September-October). During these periods, you'll find pleasant weather and fewer crowd.

Route and Accessibility:
In Portugal, travelling between cities is quite easy and affordable with well-connected highways and train routes. Start with Lisbon, then take a train for Coimbra, then to Porto, and finally to Faro which is in the southern part of the country.

Accommodation and Booking:
For the best stays, consider booking your accommodations in advance through trusted platforms like Booking.com or Airbnb. Lisbon and Porto have a wide range of accommodations, from budget hostels to luxury hotels. In Coimbra and Faro, options may be a bit limited; however, they do offer comfortable lodgings.

Clothing and Essentials:
Pack light layers for warm days and cool evenings. Don’t forget a good pair of walking shoes as you’ll likely be doing quite a lot of it, especially on the cobblestone streets. Also, carry sunblock, sunglasses, and a hat for protection against the sun.

Health and Safety:
Portugal is generally safe for tourists. However, like any other tourist destinations, be cautious of your belongings at all times to prevent petty theft. Since you'll be traveling through different climates, keep essential medications and a basic first aid kit with you.

Local Etiquette and Respect:
Portuguese people are friendly and welcoming. While tipping is not mandatory in Portugal, it's appreciated. Respect local customs and cultural sites, try to learn a few basic phrases in Portuguese, as the effort is always appreciated.