Can you go to a P195 60 R15 with all-season radials on new wheels on a 2006 Focus with original P205 50 R16 summer performance tires?
Yes you can. Search online for a tire calculator and you can
compare sizes and how much it will be 'out' by (size and speed).
You don't want anything with more than 5% difference, going from
205/50/R16's to 195/60/R15's (which I did for my focus) is only a
difference of 3%