18 to 20 weeks for standard breeds, with variations for individual birds.
You can get wooden eggs at craft stores for a nominal charge. They also work well if you are trying to trick a hen into going broody.
The roosters will, in general, pay the most attention to the hens that are most sexually mature. However, some roosters have favorites, and that sometimes has nothing to do with fertility.
I've never had a problem with my hens laying anywhere but in the nesting boxes, but I have plenty of friends whose birds lay in all sorts of funny places. You may even get a surprise - my sister thought she had lost her favorite Buff Orpie to a predator 2 years ago, only to have her reappear one morning with a group of assorted babies. Apparently she had been encouraging several hens to lay eggs for her in her clandestine spot!
Have fun - there is nothing more exciting than that first egg!