Finite-element calculations of the Brillouin gain spectrum in photonic crystal fibers (PCFs) with cores incorporating random arrangements of regions with discrete acoustic velocities are presented. The peak Brillouin gain coefficient for PCFs with cores with an acoustic domain size of $\sim 0.26\mu {\mathrm{m}}^2$ and an acoustic velocity variation of 3% was calculated to be $3.3\times {10}^{-12}\mathrm{m}∕\mathrm{W}$ with a Brillouin gain spectrum FWHM of $280\mathrm{MHz}$ . This corresponds to a decrease in the peak Brillouin gain coefficient of $7.4\mathrm{dB}$ relative to a PCF with an acoustically homogeneous core.