PR is the fruit of your SEO labor. It's not related to traffic, if you're able to place your main targeted keywords up to page 1, you should be able to get high traffic. I think It still depends on the keywords you use. SB sites, blogging and blog commenting do help a lot for traffic generation. Good luck!
PR is not really worth anything when looking at traffic from SE's. You should focus on link building and target your keywords to gain better SERP's. Once you top top10 or better for your keywords the traffic will come ;-)