Definitely not a hummingbird clearwing. Posting what state it was found in might help with the ID.

It is a sphinx moth so it is going to want to pupate in the ground.

The vine looks like Clerodendron spp

Below is the website that lists sphinx moths by state. Since you are zone 10, I thought maybe you are in Florida. I looked at all the Florida moths in the Sphingini tribe but did not see your caterpillar. Four more tribes to go but since I'm not sure what state you are in, I'm going to bed. :D

Here is a link that might be useful: US sphinx moths by state

Thanks for the help! I am in Florida. South Florida (Fort Lauderdale) to be exact. Now I am guessing it's a "five-spotted hawk moth," but still not sure. Yes, the vine IS Clerodendron, thanks! I was having trouble remembering what the name was! It's so pretty.

Using your link, I think it's now a Manduca Rustica, or a Sphinx Hawk Moth. What do you think?

Manduca rustica made me look twice yesterday but I decided that was not it. Looking at it again, I'm not going to tell you that you are wrong.

Are you able to post a dorsal picture of the cat?

It looks very much like M. rustica/rustic sphinx caterpillar to me. The only hornworms I've ever seen with purple on the sides, plus sandpaper areas on the body are rustic sphinx moths.

The vine might be coral vine/Antigon leptopus. It comes in a great variety of colors. I can't think of the most commonly used host plants for rustic sphinx moths, but I remember finding one on my gardenia bush.

Sherry

Does this have purple on sides? I guess if it's purple, it's not that bright. Here is another photo of "Monterra" (my daughter named her).

And another. Thanks again for all the help! I grabbed a few more branches from the vine I found her from, just in case.

By the way, these are the flowers from the massive vine I found her on. I was told this vine does come in a few colors. I was making a bouquet when I found the visitor on one of my cut branches!

I can't see purple in the most recent pictures you posted, but I can definitely see it in the first picture - it's just a narrow strip of purple along the yellow, triangular bands on the side. Rustic sphinx moth caterpillars are the only ones I've ever seen with purple. They get real big, as big or bigger than tomato or tobacco hornworms.

The last pictures of the vine convince me it's not coral vine, which has heart shaped leaves, with a different texture than the ones your caterpillar is eating. It's probably a tropical vine of some sort. Regardless, if the caterpillar is eating it, then it's the appropriate host plant for that particular caterpillar.
Sphinx moth cats go underground to make their pupa. You can offer it a bucket of clean, dry leaves instead, when it starts making its 'run' - I've done that before, successfully.

Sherry

How is the caterpillar doing?