How do you read signs or talk to people on the main maps?

You can't talk to people on the map the only people you can speak with are the ones inside huts, rooms, ect. sorta like Zelda 1

to read signs and such you need to buy a hand scanner from one of the shops at the starting point they open after you talk to the elder just enter the first open tent you see at the start and the rest should open.

You will need money for the scanner and I also recommend buying the translation software before entering La-mulana/the ruins you can get money from breaking vases and such, just watch it when inside the ruins themselves some rooms have a weird eye on the walls that will zap you with lightning if you "break things" save for a certain thing or in a certain order.

Thanks.

Cool game reminds me of Montazuma's Revenge/Return (GBC), with a bit more Castlevania-esque style combat, and Metroid item collecting.

No problem, one last tip before you go exploring the other era's pick up the Holy grail(a item that allows you to warp from area to area) first this will help you avoid certain traps in the later areas of the ruins. You can pickup the grail by going through a "fake" wall with the skeleton leaning against it in the room with the three block puzzle(you will only see two blocks at first if memory serves) which is right of the area with the two red skeletons in the Gate of Guidance area of the ruins just make sure you mark locations after you get the grail by reading the "grail" tablets you know you did it right when you see them glow and you see the words "Quick save" pop up then you should be able to warp back to said locations by going into the pause menu and then opening the grail warp menu

Ya, I found that Grail on my own. Skeletons give nice tips!