Hello there! It sounds like you have an exciting trip planned to Costa Rica. Here are some travel tips for your journey.

Best Time to Visit:
The best time to visit the Costa Rican cities of Alajuela, La Fortuna, and Manuel Antonio is during the dry season, which typically runs from December to April. During this period, you'll experience less rainfall and enjoy more sunny days. However, keep in mind that this is also the high tourist season, so it may be a little crowded.

Route and Accessibility:
International visitors usually arrive at San Jose's international airport (Juan Santamaría International Airport), which is very close to Alajuela. From Alajuela, you can take a direct bus or hire a taxi or private transfer to reach La Fortuna. For reaching Manuel Antonio, it’s best to go by road, either by bus or car, from either Alajuela or La Fortuna.

Accommodation and Booking:
There's a range of accommodation options in these cities from budget hostels to luxurious resorts. It's advisable to book your accommodations in advance, especially during the high season. Websites like Booking.com, Airbnb, and local tourist agency sites can offer good options.

Clothing and Essentials:
Pack light, breathable clothes as the climate is generally hot and humid. Bring a good pair of walking shoes and don't forget your swimwear. Sunscreen, insect repellent, a hat, and a reusable water bottle will be essential. An umbrella or rain jacket can come in handy if you are visiting in the rainy season.

Health and Safety:
Remember to stay hydrated and use sun protection to prevent sunburn. Depending on your activities, consider vaccinations for Hepatitis A and Typhoid. Always follow instructions and signages in national parks and beaches for your safety. Travel insurance covering medical emergencies and evacuation is advisable.

Local Etiquette and Respect:
Costa Ricans, known as Ticos, are generally friendly and polite. The common greeting is a firm handshake. Casual attire is acceptable in most places. Tipping is customary in restaurants and for services. Environmental conservation is a big part of Costa Rican culture, so respecting nature and wildlife is very important.