Two weeks ago I had surgery for a left inguinal hernia and hydrocele (marsupialized). The left testicle is now positioned at the top of the scrotum. Will it drop into the normal position later?

Maybe. You may just be experiencing swelling that has caused the retraction on the testicle. It should drop back into place. If it hasn't recovered by around 6 weeks post-op, see your surgeon. Btw, you should call him with your concerns.
Maybe. The wound is still healing and there is a lot of inflammation present two weeks out from surgery. It may loosen up and drop with time. It will probably be better after 6 weeks or so, but i would wait 3-4 months before worrying too much.
It should . Feel free to pull it down as well. Doesn't sound like anything is wrong, but be sure to ask your surgeon when you see him/her for your postop visit.