It's not espeak, it's flite. I had the same problem before espeak was available and flite was the only option. I hacked it by making a shell script that modified the output path to pipe it through to a player. So flite thought it was putting out to a wav file, and the "player" was reading it from stdin. Kind of a hack (and caused a slight delay) but it was usable.

Once the normal espeak came out (and worked) I disabled the hack and went on from there. Good luck!