Sure, here are some travel tips for you:

Best Time to Visit:
Visit Colombo, Jaffna, and Galle during the dry season, which is between January and April. The weather is pleasant, making it ideal for sightseeing.

Route and Accessibility:
The most convenient way to travel within Sri Lanka is by train or bus. From Colombo, you can take a train to Jaffna and Galle. Buses are also readily available and are a cheaper option.

Altitude and Acclimatization:
All three cities are at sea level, so altitude sickness won't be an issue.

Accommodation and Booking:
There are a number of accommodations to suit different budgets in these cities, from guesthouses, hostels, to five-star hotels. Make sure to book in advance, especially during the high season.

Clothing and Essentials:
Due to the tropical climate, bring lightweight and breathable clothes. Don't forget your sunblock, shades, and a hat to protect yourself from the sun.

Health and Safety:
Avoid drinking tap water; always opt for sealed bottled water. Ensure your vaccines are up to date before your travel, and do carry a basic first aid kit.

Local Etiquette and Respect:
Sri Lankans are renowned for their courtesy and hospitality. Respect the local traditions and customs. When visiting temples, cover your shoulders and knees. Never touch anyone with your feet or point your bare feet towards them as it's considered offensive.