Hi rubius,
I guess it's a topic that doesn't get much attention since the pain of fissures pretty much kills any thoughts of sex for most people. I think it's a really good sign that you're even thinking about it!
I don't really have much to offer in the way of experience to help you out, but I can speculate a little . Hopefully someone who has experienced LIS will jump in here for you.
I don't know if there is really a set time frame, and of course it's a question best addressed to your surgeon since everyone's healing times and progress after surgery are different, and it's best to get your doctor's advice. For women of course it is a bit more of an issue than for men. I would think it wise to make sure the incision site has fully healed, that there is no longer any drainage or bleeding from the wound. Davo in his surgical post said that for him the incision site was fully healed at 10 weeks.
It might not be a bad idea for both you and your partner to shower prior to intercourse to decrease the amount of bacteria that naturally resides on the skin, and it would probably not be a bad idea for you to clean after intercourse for the same reason.
As far as how much pain to expect, you probably want to take things really slow and gentle as you get back into sexual activity and see how it goes. You may also have to experiment with positions because some positions may put too much pressure on the posterior to be comfortable for you.
but who knows! You might find out that it's all smooth sailing and starry skies right from the start!
I'm so glad to hear you're feeling better and thinking about other things in life that are far more joyful to contemplate!