Personally i do this ALL the time lol. Yesterday i was smoking a fat one, walking through leicester square, on my way to empire casino to play poker.
I smoke everyday, and have been doing for years. At first it was great, then after a few years i've realised moderation is the key, because the weed you get in london these days, is 'sprayed', and very high in THC. If you smoke this weed everyday, it will have negative effects on your life. That is all ill say on this matter.
But yeh, back to the point. On a punting day, ill leave my house with 2 joints strapped (just incase a WG flops on me for whatever reason).
Usually ill smoke like 5-15 minutes before i meet her. I always do worry about whether they would reject me because of the weed smell ect, but so far no WG has even commented anything related to weed. I think generally, people prefer the smell of weed to the smell of ciggs, but i could be mistaken.
Anyways, weed can make you VERY VERY horny, under the right circumstances. For example, weed can make your dick more sensitive. It has stimulant properties in terms of dopamine-release, similar to cocaine or meth, but obviously nowhere extreme as those hard drugs. But it also has serotonergic-releasing properties, which is similar to how you can't get a hard-on when drunk...
I guess it would depend on the persons brain chemistry, and even the weed. Some people may smoke, and they become very withdrawn and introverted, whereas others will become the opposite.