Calls in Mexico

I know I pay by the minute for calls in Mexico.

From US cell phone to US cell phone in Mexico do you have to dial +1 or just 1  or just the 10 digit number?

From US cell phone to another US cell phone while both are in Mexico do you have to dial +1 or just 1  or just the 10 digit number?

Finally calling the US from Mexico on US cell phone do you have to dial +1 or just 1  or just the 10 digit number?

Same questions for sending a text.