To me the "Bbsus9" is another way of saying the chord is a Bb11. You can create an 11th chord by using chrisbell's spelling of F, Ab, C, and Eb or abbreviating it by playing Ab/Bb as LadyChen suggested since the 5th of the chord is expendable unless it's the melody of course.
Concerning 11th chords: I never include the third in using 11th chords but sometimes I see books that go ahead and use it in theory. Sheet music that I've seen never includes the third unless the chord indicated is a minor 11th chord. To include the third just doesn't sound very good to me. Does anybody have a opinion on this?
The notation Bb11 is confusing. I've seen it more and more in pop music and I always have to explain to students that it's not a legit notation. Maybe I'm just old school but chords are built on thirds. Bb11 should include the major third and the natural eleventh. But that is clearly not the intention (in my experience) for the chord. Bbsus9 is correct. Minor chords have natural elevenths and major chords have # elevenths. The nat eleventh obscures the function of the major third.
On the other side of it, Bb13 should also technically include the natural eleventh right? But who does that? And we see that chord all over the place. Go figure.
Now all that said I think you can play whatever you want. And if you mean Bb11 (with the major third), then go for it.
