I agree with the others, this sounds like : Concert Band
Better than clothespins is a plexiglass sheet to cover the music and prevent it from blowing away. Hardware stores have them and can cut them to size for you (ie. 12"x18")
Also use a heavy music stand, as the light weight ones can be tipped in light wind.
Yes to bug spray.
Bass guitar works well in concert bands, the frets give a stability of tuning the rest of the band can lean on.
If you're doing it on upright, I'd say stick with pizzicato all the way, until your comfortable with the arco playing sections.
Consider that possibly the main reason you're there (string bass), is to provide the pulse and drive, that the tubas (and bari sax) cannot provide. They can't drive the band walking. Too much air, needing to breath, the latency... = no drive in 4. (In 2, yes, but not in 4)
The string bass brings that, in ways the others cannot.
They can do the volume swells, and long notes, the majestic, so you can lay off that until you're ready to do it.
They will lay off the walking, and the riffing, because you'll be there.
The tubas will also rip through Sousa, while you're fumbling to decipher the notes at pitch. But you'll burn through the jazz, rock, pop, while they take breathing breaks or feathering around you.
Another thing, yes watch the conductor, and yes blend well with the tubas, however, in the jazz/pop music you'll play, the string bass role is to be the front end of the attack, to be the pulse slightly ahead of the beat to drive the lumbering bus forward. Don't hang back in the beat with the tubas. You're there to drive.
YMMV.
Enjoy!