Hi Mike - welcome to the hobby,
Local noise tends to be more problematic on the LF bands.
My own experience of operating in an urban environment. Is that you need to work you way through a number of different noise sources and solutions to reduce the overall noise floor.
Before buying an noise canceller, which will only help under certain circumstances. I'd suggest doing the following:-
Try and reduce the amount of noise being generated in your own property first. A quick test is to power the radio from a battery and flip the main breaker. if nothing changes that's great. But the chances are you will find one or more sources of unwanted noise are actually being generated in your own home. So the next stage is to do some direction finding with something like a portable receiver or loop antenna, and track down the sources. Cheap wall-wart switched mode supplies and phone chargers are frequent offenders.
Suitably applied and sized ferrite rings can help a lot to tame this sort of interference source.
Some of my experiences are documented here:-http://webzoom.freewebs.com/g8jnj/EMC%20and%20Amateur%20radio.pdf
Once you have sorted out your own home. I'd take a look at your antenna. Adding a common mode choke to the G5RV coax just below the open line section can make a big difference to the level of received noise on the LF bands. However many commercial designs and those published on the internet. Do not provide sufficient choking impedance to make a difference. Especially on the LF bands. A few turns of coiled coax as recommended by many. Will make NO DIFFERENCE !!!
Take a look at the choking impedance charts on Steve G3TXQ's website and pick the most suitable design for the frequency range you are interested in. Personally I always try to get as much RESISTIVE choking impedance on the LF bands as possible. As locally generated noise seems to be much less problematic on the HF bands.http://www.karinya.net/g3txq/chokes/
Once you have sorted out common mode induce noise on the coax. And the G5RV is working more like a truly balance antenna. You may be able to try changing its orientation slightly so that the worst noise sources lie within one of the nulls off the end of the antenna.
Once you have worked your way through these issues. You will have a much better idea about what other noise sources are likely to be local to you, or your neighbours properties. How to trace them, and if it is possible to do anything practical to fix them once you have found them.
Only when you have investigated all of the above. Would I consider it to be worthwhile looking at noise cancellers.
I hope this helps - Good luck,
Martin - G8JNJwww.g8jnj.webs.com