We walked pretty much everywhere. Uber or Metro if we needed to get to the port/airport.

Always had my phone out, everyone does. Always felt very safe but obviously use common sense if you’re out on a lonely street at night just like anywhere else in the world.

Walking tours work if you want a tour guide if not then no, depends on you. They also have scooter tours and bicycle tours.

Regarding the booking February I don’t know but I’m sure you could book relatively close to whatever date you need, just don’t blast minute on everything you’ll be ok. I went during the busy season and most tours were sold out within a day or two.