I couldn't find exact numbers, but I can give a relatively reasonable estimation.
Last year marijuana use in Colorado, where it's legal, by individuals 12 and older was at 12.7 percent (specifically this is percent who used within the last month, which is pretty good estimation of those who desire and support actual use of it). This was last year before distribution went up, new studies haven't come in yet; however, preliminary studies suggest that the number has not increased much with easier distribution; so likely still about 13% use.
However in the us 58 percent support legalizing marijuana. and 55 percent of Colorado supports the law.
So if we make a small presumption that Colorado is roughly indicative of the rest of the country then it looks like more then 40% of Coloradans support legalized marijuana despite having no desire to use it. This also means only around 25% of those that support marijuana legalization have a desire to use it.
Not as good as an official Gallup poll, but should give you a good rough estimation for the percentages.
And of course as I said I personally wish to legalize it. I don't want anyone to smoke it, but making it illegal does too much harm, in expense to the government that must fund prosecution of it (and lose tax on it), harm to individuals who suffer absurdly disproportionate punishments for it's use, and harm to society by creating a criminal black market for it which leads to encouraging other crimes. The harm of allowing people to freely use marijuana is tiny, the harm in trying to prevent it huge; thus the reasonable choice is to legalize it.
Besides, all things being equal I prefer to allow people the freedom to make choices, even ones I don't personally encourage, so long as they are not doing harm to others or substantial harm to themselves, and again marijuana just doesn't do that much harm. People need to be free to make that choice.