wireless paths crossing

No, not if you do it half way responsibly. Choose the channel farthest away from them. In fact, if they are using 6 ask them if they'd mind to choose either 1 or 11 and you'll take the other so there would be as little chance of interference as possible. You can also go to horizontal polarization if they are on vertical to further reduce interference.

It should be no problem at all if:

1. They are on a different channel or frequency.
2. You also use parabolic dish antennas to minimize side lobes.
3. There are no reflections for nearby buildings. Think billiards.

Crossing paths does not "mix" the signals in mid air, so there's no interaction. The narrow beamwidth of the dish antennas will keep the radios from seeing each other. Putting them on different non-overlapping channels (1,6,11) will prevent interference even if the antennas do see each other. Reflections from building can screw up the works.

At 300ft, it's more likely that you'll have an overwhelmingly good RF signal level and therefore will not be very susceptible to interference. I can't say the same for the other user, who may receive more interference from you than they create due to the differences in range. One thing for sure... you're committed to using directional antennas (panel, patch, or dish) to avoid interference.

: Will this prevent my connection from working?

Simply - it's gonna be working. But don't forget to set a different channel.

m.