I don't think the sign is in the neon museum.

The Money Tree was on the Strip at 2456 Las Vegas Blvd...which I think is the Plaza on the corner of Sahara, where The Bonanza "The World's Largest Gift Shop" is currently located. Yup...just confirmed that on the Vintage Las Vegas Site.

There are a couple more pictures on the Vintage Las Vegas site...here:

http://vintagelasvegas.com/search/Money+Tree