Currently 80% effaced and 3.5cm dilated

My dr told me i need to come in ASAP as soon as i start having contractions since baby head is “impressively low” and doesn’t think it’ll take long at all. I have a 4 year old daughter I’ll have to drop off with my parents and i also live about 45 mins away from the hospital. Not that they don’t think I’ll make it in time but, I’m worried i won’t be able to get a hold of my parents easily. If you HAD to guess, when should i expect labor? I know you can be 3cms dilated for a whole month and still not go into labor until day before due date (this happened with my daughter) but any guesses? Does 100% effacement usually mean labor will start?