LLoyd,
You can certainly make some very tasty cheese without a pH meter. However, you may not always get the "right" texture. A good example: I never could get my Goudas to the right texture until I got a pH meter. The recipes called for pressing overnight, but that was WAY too long - at least with the cultures I've used, the target pH has been reached in a couple of hours. Leaving overnight resulted in a far more acidic cheese. Tasty, but crumbly and rather cheddar-ish rather than smooth and pliable and mild. But my last two Goudas, with the help of the pH meter, came out of the press at 5.3 - 5.4 pH, and they have been exactly right as far as texture and flavor. Of course, different milk, different cultures, different make sizes ... YMMV!