You would want to call ahead to let them know when you want to come. Oftentimes they have to clear it with the abbot. You could probably refer to the abbot as "Father." As for talking to the monks and nuns, that depends. From my limited experience you can usually talk with them, but I've been to one women's monastery where the nuns generally didn't speak with guests, except one nun who was designated as the person to talk to people. Staying after liturgy should usually be okay. There may be a meal, which might be shared with the monastics, or you might eat separately with other pilgrims. You may be asked to help out with some labors at the monastery, or you may be allowed to go about the grounds, read, or pray in one of the churches or chapels. There might also be a bookstore for you to peruse. But whatever you do, make sure you ask about it first.