Sure, I'd be happy to provide some travel tips for your trip to Colombo, Anuradhapura, and Polonnaruwa in Sri Lanka:

Best Time to Visit:
The best time to visit is between January to March as the weather is generally dry and sunny. Do note that Sri Lanka has a complex climate, so these are just guidelines.

Route and Accessibility:
Colombo is well connected by flights, and you can travel to Anuradhapura and Polonnaruwa by train, bus or private car.

Altitude and Acclimatization:
These locations are not at very high altitudes, but if you're travelling from sea level, it might take a bit of time to adjust.

Accommodation and Booking:
There are plenty of accommodation options, ranging from luxury hotels to budget hostels. It's advised to book in advance particularly during peak travel season.

Clothing and Essentials:
Light, breathable clothing is suitable for Sri Lanka’s tropical climate. However, do carry a raincoat or umbrella. When visiting temples, dress modestly and remove your shoes before you enter.

Health and Safety:
Stay hydrated and use sun protection. The food is safe to eat but if you have a sensitive stomach, avoid street food. Stay cautious of your belongings in crowded places to avoid theft.

Local Etiquette and Respect:
Be respectful of the local customs and traditions. In temples, it is necessary to cover your shoulders and legs, remove your shoes and hats. Don't pose with your back to a Buddha statue (it's seen as disrespectful).