No, I mean their fleets are so small, that there is no reason to do it. It wouldn't be hard to fully many every Klingon warship with Klingons. There are so few ships, it should be easy. And we know the reason so many humans are seen: it saves money and time on make-up.
O RLY?? Let's look at some math, shall we?
We saw, what, a total of like 15 possible
Galaxys, right? OK, 15 x 1000 = 15,000.
Numbered starbases: about 630. Give each starbase about 1500 personnel. 630 x 1500 = 945,000.
Unnumbered starbases (DS9, K-7, etc.), outposts, planetary facilities: figure about 1 million personnel assigned to them.
Ships...well, we're working with small fleet numbers here (I'm a large-fleeter, my own self), so let's say 7000 starships of all types, with an average crew of 500. 500 x 7000 = 3,500,000.
3,500,000 + 1,000,000 + 945,000 + 15,000 = 5.46 million active personnel at a conservative estimate just for Starfleet, using small-fleet numbers & not taking into consideration reservists, inactive or otherwise. This would make Starfleet nearly 2½ times the size of the PLA (the largest army currently on the planet); 3.8 times the size of the US military; 7.12 times the size of the Russians. (NOTE: for current armies, I used only active military numbers)