In last February-March I did my Patagonian trip - Chile plus Argentina. It was excellent, but I'm in doubt if it can be wise to go South of Bariloche in late April-May, because I've heard from people who have been there in May that they were frozed. In a bad weather with a low clouds it can be disappointing to see the wonderful mountains of Tierra del Fuego and Patagonia.

So, my recommendation is to go to the North with a spectacular Atacama desert (geysers, geogliphs and altiplanos - not so hot at these high levels), Arica area (Lauca Park), Salar de Uyuni in Bolivia, the Andean range from Salta to Mendoza in Argentina. Still, you can enjoy the wonderful coastal towns of Chile as Lisboa-like Valparaiso, Vina del Mar, La Serena. I think that this circle trip can be good. Even if the temperatures at the high altitudes are not high, the visibility is quite good thanks to low level of precipitation. Another suggestion is Easter Island, though the end of April is an end of the recommended season. By the way, this time is an excellent one for tropics - so, you can probably have an air jump to the Argentine-Brazil border of Iguazu waterfalls.

Enjoy your trip, Alex in Jerusalem