Day 1
Arrive and settle
Use San Salvador for your first night, meals, and onward transport, or transfer directly only if timing is easy.
Day 2
Volcano or lake focus
Pick Santa Ana Volcano for adventure or Lake Coatepeque for a softer scenic day.
Day 3
A final coast stop, if your flight allows
Add El Tunco or a coast sunset if it fits your flight and transfer timing.
What to leave out
Save the other regions for another trip
Ruta de las Flores and Suchitoto are better saved for a longer route unless they are the main purpose.