the pokedex don't normall reveal the gender unless you've caught the pokemon and unless they really have physical differences its all but hard to tell except for experts that can note even the slightest changes. so unless you're picking or looking between the legs which is really the only way the general people could tell then I'd say no as just like with normal animals people generally can't tell the gender.

If we're going for semi realism then it makes sense we wouldn't be able to tell unless you're a pokemon biologist expert.