Regular pre-K in Tennessee is for kids that turn four years old before the end of September. For my special education class, a child is eligible when s/he turns three. This past year, my youngest student joined my class when he turned three in March, my oldest turned five last November. Children are refered to my program by their pediatrician when he judges him/her to be "at risk", that is, short of their developmental milestones.
Your son is not really behind with toilet training; boys start later and take longer; my oldest son, now almost 12, was more than three years. My daughter, now 3 1/2, was completely trained at 26 months. My youngest son, 20 months, is just starting to give signals that he is wet, and we have to be looking for those signals to notice. If your boy is actually letting you know by getting your attention, you are doing well.
Incidently, since my wife and I are raising ours bilingual, initial onset of language is later, but once they start, (or in the case of the girl, when she started), they catch up quickly. Feel free to see my family at
www.myspace.com/xrayagent.