I've placed orders for around 15 condors over the last few days, and only two have filled.

Whoa! Wayyyyyy too many. What's your hurry, Buckaroo? Ease up!!! If the market starts to assail your positions, you're going to end up totally deer-in-the-headlights, with no plan, no clue, no hope, and then, no account.

Keep those two ICs you placed, and wait until you've gotten your nose bloodied a bit and come through 'just fine' or better, before you go cranking volume.
Second, how/where were they filled/targeted? You've not told us anything about a) what you're trading, b) how far out in time c) how far away are your short positions d) how far apart are your legs, or e) whether your individual legs are on major strikes (which get major love) or unknown strikes that might get a quarter of the expected daily volume for that area. Is your IC's delta balanced? Biased high or low? We don't know.....
I've adjusted my approach to make sure all legs of the condor have volume, but still not getting much traction. Does anyone have any suggestions?
Am I going to have just as much trouble exiting the trade if I want to exit before expiration?
In general, vertical spreads will get better pricing than individual legs. But as far as ICs go, I always put up the vertical legs first, I enter something 1-tick inside the offer (to get everyone's attention -- this might cut the BID-ASK spread in half instantaneously), then I compare their joint price to the IC market, and work things from there. Sometimes (SPX or the 24-hr ES) I get better pricing on the verticals -- especially a thin (or far-off) market that has volume so poor you've got to entice them out of the corners to play. And sometimes, I get an immediate "Plunk!" on the IC -- and at a better price than I might've gotten for the individual legs. (Less common, that. But it makes me smile when it happens.

)
On occasion, I've given up, and written 1 side (in the direction of a market move), expecting a change of direction the next day or two. Especially in times of shitty VIX, flexibility here means you're not so trapped by a 10-12 VIX through Wednesday evening, only to find a 14 VIX come Thursday morning...

One thing to note: a commonly played-up trait of the ICs is that as value increases on one side, it will symmetrically decrease on the other, and so the only net on the IC's value over time, is time itself, ticking slowly, slowly away. IN FACT, the curvilinear nature of options valuation means that,
with a big shift of the market (up or down -- doesn't matter), the effect on the top side will be different than the effect on the bottom side, and this will affect the value of the IC (i.e., its
profitability 
) to an increasing degree, as expiration approaches. BE AWARE.