I agree with parts of what everyone has said.
Most people write R things and things such as human-pokemon relationships to be OMGcool or risque, and, IMO, that's a silly thing to do, and the fic won't turn out well, and you'll look stupid. More often than not, a sex scene isn't in any way necessary to a fic. Like Keleri said, implied stuff is often just a better route to take. You could take it out, and life will go on.
That said, I really find the idea of human-pokemon relationships interesting. *pokes her fic* I didn't know anyone else did o.o;;
If you think about it, ledgendary pokemon can assume hman form... so would it be so farfetched for one to have a fling with or-- OMGtaboo-- fall in love with a human? When you get down to lesser pokemon like pikachu or rattata, I agree with not_awake that they are, in fact, just animals, and it's really sort of weird to see something with a eevee mother and a human father (which I've seen, and the fic sucked). But for pokemon like the ledgendaries, or humanshape ones, I guess the question comes up: Could they be considered a type of human? If you want to get into the science of it, it's have to be true for them to be able to breed in the first place.
I've always thought about that *shrug* and even moreso as I've gotten deeper into my fic.
But like I said, there's two ways to do it: the way in which you glorify the sex because it's OMGseckss!!!1one, and the way in which you glorify the relationship (and character development). The latter is much more appealing to me. *shrugagain* And like I said, is it fundamental to the fic to do a whole scene, or will life go on if you just allude to it?
Anyway, the context of the question sort of offsets me. I love the humanxpokemon genre, but I hate the way people try to do it. Trying to push the limits and write as gruesome and explicit a fic as you can possibly isn't too... good, IMO. It's like the difference between artistic nudity, which is totally cool by me, and some kind of porno. I know there are people who like lemon-lime, and to each their own, but here lies my opinion.
*shrugagainagain*