What height can you ride a 29er?

Answer 1

29er is silly marketing speak for 28"/622 mm/700C wheel size, which is the same as for most "adult" sized bicycles - only with knobbly MTB tire treads.

If you're big enough for them, you're big enough for a 29er.

Do note that the MTB trend calls for sloping top tubes, so although you might be doing fine in terms of standover height the bike might still put in a too stretched out position fofr comfortable riding. For utility purposes this can be helped by going to a shorter stem, but if you're looking for serious performance you might want another bike.