Can I drive my sisters vehicle in to Mexico If the car isn’t registered in my name?

Yes if you don't go where you normally need a auto permit - which is most of the mainland past 21km. Baja and Sonora you don't need permits.

The problem is getting insurance for you in her automobile. Not a good idea to drive in Mexico without insurance

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The US does not check for ownership of the vehicle … but might ask for ID

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Answer:
Check with the hotel where you’re staying. I have heard you don't need a sticker in Baja but I would double check. It depends on where the Hacienda is located in relationship to the resort. If it is on the highway before the resort, you have to get a car sticker and you must be shown as one of the owners on the vehicle. The problem won't be getting back into the US, it will be driving around in Mexico.

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Answer:
No, there’s no problem at all if you don´t go farther than that.