Hi,
I guess it would depend on if you were composing for the entire movie really. Different movies have different scores at different parts of the film at different tempos to match/ compliment the different emotional settings of the film.
And I think you'd look at the length of the film as an indication, not the frame rate. All 29.97 will tell you is that there is best part of 30 frames per second... not how many seconds of film there actually are.
I don't know how to calculate tempo to a 29.97 frame rate - infact I don't think it's possible as Tempo relates to BPM and seconds and time and frame rate use a different measurement really.
In Logic view 'Bar + Time' In the Bar Ruler (small clock and musical note icon on very right of bar ruler).
You might want to get a feel for how fast or slow you'd like the soundtrack to be for certain parts of the video as Yadj suggests and have the music match the video and not the frames.
As Rounik and YADJ said before, you won't calculate the tempo of the music with the frame rate of the video.
Do you have Logic ? Personally, I prefer to score music to picture with Logic rather than SoundTrack Pro.
One feature I can't live without is markers.
I always like to add markers to define the main cut points of the movie. I then time-lock the Marker list so that any tempo changes I do won't shift the markers positions (Options > Lock SMPTE position in the Marker local menu). I then use Beat Mapping to calculate the tempo with precisions between scenes.
By the way, how long is the video you want score ? Scoring music to picture is a broad subject... tell us if you need some tips!