I know there is a bus from Valparaiso to Santiago, but unsure of the specifics.

In Valpo we're staying at Voga Exclusive Guesthouse. I'm guessing we take a taxi from there to Bus Station? We'll ask the hotel to call for a taxi.

In Santiago we're staying at CasaSur Charming Hotel . Again, We'll probably take a taxi from bus station there. Do we just exist to street for taxi in Santiago at the bus station? Is there more than one bus station?

If you take a Turbus bus from Valparaiso and stay on until their terminal, Terminal Alameda, they have a taxi rank inside the premises. There are more bus stations but the one across the side road, Terminal Santiago, is where the other buses will stop.'

Your lodging is very close to Santa Isabel metro station on line 5. If you want to do the whole thing by metro (not fun with luggage) you could get off any of the Valparaiso to Santiagobuses at Pajaritos station on the edge of the city and get on line 1 of the metro there. Stay on it until Baquedano station and switch to line 5 there. But don't do this with suitcases or at a busy time of day.

Thanks. We'll just grab a taxi at the bus terminal (i'm guessing either Terminal Santiago or Alameda are ok) . Do taxis just take local cash, or do they take credit cards, or even USD?

Local cash only. Make sure you know the value of the bills and have enough small ones to pay the taxi.