Trying to find train or bus from Aix to il sur la sorgue without any luck. Has anyone done this ? Appreciate any advise.
The rail station for L'Isle sur la Sorgue also serves the small town of Fontaine de Vaucluse and shows up on some websites as "L'Isle-Fontaine-de-Vaucluse". That's probably why you're not finding rail service.
Taking a train the entire way will probably involve a convoluted routing that includes a TGV to either Marseille or Avignon, which will make the trip rather costly and likely still slower than a bus following a more direct route--if such a bus exists. I haven't turned one up, but my internet service is misbehaving at the moment. Try Googling: bus Aix-en-Provence to L'Isle-sur-la-Sorgue and following the first 5 to 10 links.
Bus schedules are highly day-of-week sensitive, so it is key to specify an accurate travel date.
From personal experience I can tell you that it's relatively easy to reach L'Isle-sur-la-Sorgue from Avignon.
It's served by LER bus route number 17 - current timetable here. Note that certain journeys run on specific days: "tous les jours" is "every day", "sauf dim et feries" means "does not run Sunday or on public holidays", "lundi" is Monday and "vendredi" is Friday.