1. It all depends on your interests. Most people spend just a day or two, but I kept busy for five days exploring the Malecón 2000 and Malecón Salado, Cerro Santa Ana, Manglares Churute nature preserve, Cerro Blanco, etc. Look at the Things to Do tab at the top of the page (which is what I did) and see what interests you. We can help you narrow it down.
2. About four hours by bus.
3. The web site latinbus.com seems to be undergoing a transformation. It detours to andestransit.com now. It will tell you bus lines and schedules.
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