Hello! It's great to hear you're planning a visit to Buenos Aires, Montevideo, and Rosario. These cities are rich in culture and have lots to offer. Here are some travel tips:

Best Time to Visit:
The best time to visit Buenos Aires, as well as other cities like Montevideo and Rosario, is from April to June (Autumn) and from September to December (Spring). The weather during these periods is typically mild and enjoyable.

Route and Accessibility:
You can start your journey from Buenos Aires. The city is well-connected with major airlines worldwide. From Buenos Aires, you can take a ferry to Montevideo which typically takes about 2-3 hours. Lastly, you can reach Rosario from Buenos Aires either by bus or by train, which usually takes about 4-5 hours.

Accommodation and Booking:
All three cities have broad choices in terms of accommodation, ranging from luxury hotels to budget hostels. It is advisable to book your accommodation in advance, especially if you are travelling during the peak tourist season. Websites like Booking.com, and Airbnb offer various options based on your budget and preferences.

Clothing and Essentials:
As the weather is generally mild, you should pack versatile layers. Don't forget your comfortable walking shoes, as you will be exploring the city mostly on foot. A rain jacket or umbrella could come in handy as well. In addition, sunscreen and a hat are advised due to the region's strong sun.

Health and Safety:
Ensure you are up to date with routine vaccines before your trip. Tap water is considered safe to drink in these cities. However, as safety conditions can vary, always be aware of your surroundings and keep your belongings secure.

Local Etiquette and Respect:
Latin American culture is quite friendly and warm. Politeness and respect are appreciated. Tipping is common in restaurants. In Buenos Aires and Rosario, Spanish is predominantly spoken, while in Montevideo, Spanish and Portuñol are used.