you for reaching out on the community and telling us about your issue. I do apologize for the issues you're having. I was taking a look but I'm not too sure about how prepaid cards work inside quicken as I've not had the chance to try setting one up for download.
As it goes for making a manual checking account yes you're able to choose Mexican Pesos as an option after you've set up the account. You can do so by after making the account selecting the account and in the bottom right selecting settings. From there you'll want to select currency and select Mexican peso.
Please let me know if this helps you out.