Good test.
I made an APK that only had the code:
openBrowser("https://play.google.com/store/apps/details?id=com.facebook.katana")
And it worked like I suspected. On my S3 (with 4.1.1) the Google Play app opened right to the facebook app.
On my S1 (2.3.1) I got the dialog window which asks if you want to use a browser or Google Play to open the link. This is what you would get if you haven't ticked the box for defaulting which app to open this specific type of link with.
So I would suggest, go to Google Play Store with a computer, either figure out by your apps APK name what the address would be or perhaps it is provided by Google prior to uploading.
Video of the S1 running the test app:
Excuse the crap quality
http://www.youtube.com/watch?v=lZAcC0BcQEY
My hovercraft is full of eels