Tom Taylor is currently visiting Munich and a couple of days ago he had a paper with Dieter Lüst and Stephan Stieberger which discusses (besides many detailed tables) a simple observation: Assume that for some reason the string scale is so much lower than the observed 4d Planck scale that it can be reached by LHC (a possible but admittedly unlikely scenario) and in addition the string coupling is sufficiently small. Then they argue the 2 to 2 gluon amplitude is dominated by the first few Regge poles.
The important consequence of this observation is that this implies that the amplitudes are (up to the string scale, the only parameter) are independent of the details of the compactification and the way susy is broken: This amplitude is the same all over the landscape in all 10^500 vacua!
Observationally this would mean the following: At some energy there would be a resonance in the gg->gg scattering (or even better several). The angular distribution of the scattering products are characteristic for the spins of the corresponding Regge poles (i.e. 0 for the lowest, 1 for the next etc) and most importantly, the decay width can be computed from the energy of the resonance (which itself measures the free parameter, the string scale).
Of course, those resonances could still be attributed to some particles but the spin and decay width would be very characteristic for stings. As I said, all this is with the proviso that the string scale is so low it can be reached by LHC (or any accelerator looking for these resonances) and that the coupling is small (which is not so much a constraint as the QCD coupling is related to the string coupling and at those scales is already very small).