I hope to start from SJPP and walk for 2 weeks, continuing more next year. Will there be many folk around from SJPP if I start midweek at the end of September? I'd appreciate seeing other travellers at first, especially on the first day.
I think that by the end of Sept you will see fewer peregrinos than you will if you started at the beginning of Sept. However, that being said, St Jean is such a popular place to start, I am sure that even during mid-week you will meet up with other people. If you ask the very helpful people at the Aceuil des pelerins (where you get your credencial) they will be able to give you an idea of how many other people picked up their credencials on your day of arrival (which will give you an idea of how many other people you can expect to meet). A lot of Spanish people start at Roncesvalles, so you are sure to meet up with people there too.
We walked in September and began mid-week (we planned it that way).
There were plenty of other pilgrims, and the alburgues were not full.
We also walked the inbetween stages - which worked nicely.
You will have plenty of company in September, no matter what day you begin!