Before my Fenix 5 I had a Forerunner 230, and on similar routes which I run now, I tend to notice that I found GPS/Glonass in the green within 5-6 seconds.
I have noticed on my Fenix 5 that it seems to take longer possibly (only say possibly because it's a long time since I had my 230).
I went on a run the other day and it took around 10-15 seconds with a few trees and today I was in an open car park without too much around me and it still took around 10 seconds to find.
I'm from the UK if that means anything to any of you.