Surely! Visiting Buenos Aires, Montevideo, and Rosario will offer you a wonderful South American experience.

Best Time to Visit:
The best time to visit these cities is during the spring (September to November) and fall (March to May). The weather during these months is relatively mild and enjoyable.

Route and Accessibility:
Flights are available to Buenos Aires' international airport from most major cities worldwide. From Buenos Aires, you can take a ferry to Montevideo, and a bus or flight to Rosario.

Altitude and Acclimatization:
Buenos Aires, Montevideo, and Rosario are all at relatively low altitudes so altitude acclimatization is not necessary for this trip.

Accommodation and Booking:
All three cities have a wide range of accommodations ranging from budget to luxury. It's recommended to book your stay in advance, especially during peak seasons. Airbnb is quite popular and there are a lot of hostels and hotels offering good deals.

Clothing and Essentials:
Temperatures vary widely throughout the year so pack layers. Always have a rain jacket at hand, as sudden rainfall can occur. Don't forget comfortable walking shoes as these cities are best explored on foot.

Health and Safety:
Standard vaccinations are necessary as per your home country's guidelines. Traveller's diarrhea is the most common travel-related ailment, so consider packing anti-diarrhea medication. Stay hydrated, especially during the summer months when temperatures can soar high.

Local Etiquette and Respect:
Respect the local culture and practices. The people are typically warm and friendly. Spanish is the main language spoken, so knowing a few basic Spanish phrases would be useful. Practice common courtesies and be mindful of the locals' etiquette. On greeting, it's common to give one kiss on the right cheek.