I have been several times. Love the people and the place. you will see how much you have in many respects when you go there. Once you are ok with being haggled to come to my house and see this.
My advice is to stay in private houses, as you will be giving the money to the private people who need it more. they have to pay exorbitant tax whether the rooms are rented or not and also they are good value. Some private homes have air con others not, just ask and say you want it.
You can also eat at private houses, but when I was there you had to order the day before for breakfast or the morning possibly for the evening meals. Brilliant food at the guest houses. Also at hotels you will be waiting forever and I mean forever.
My advice would be to stay at a hotel the first night, we stayed at hotel Lido or Lincoln the first night and then went down country by train normally and get a mix of bus and private taxi back.If you are traveling alone or with one or two others it is easy.
I always took cash, US dollars in small denominations, including lots of ones and fives.I think you can get money out from banks to ATM's, but used to be a pain.
Last time we went to Santiago in the south and then traveled west and spotted a little island off the coast. got a boat out to it, stayed the night and had brilliant food. sleep with the door open and during the night you would see guys fishing during the night.
We always took colouring books, colouring pencils, soap, shampoo, toothpaste, toothbrushes, basic meds, plasters, headache tabs etc and it would be really appreciated. a lovely people, I was only saying a couple of days ago I would love to go back.
How much are tickets now, or do you mind me ask? Not sure about visas or if you can get them on arrival. have fun.