[jeffy]

How soon do you normally start noticing signs of contamination? And is the only real way to tell by taste?

Tasting is the best way.  Sourness is a good clue, but don't confuse this with yeasty flavors of young green beer. 
Having a very low final gravity is a sign.  A thin white film (pellicle) on the surface of the beer is another sign.  A beer that just will not clear may be from infection, but not always.

[james_cornell]

So if I crack the lid at the 1, 2 and 3 week marks to take a look and taste - and then if still okay bottle and taste again, that should be a good way to determine whether or not its contaminated right?  I know it's not exact but from what I've read contaminated beer should be fairly obvious when tasting? 

[morticaixavier]

So if I crack the lid at the 1, 2 and 3 week marks to take a look and taste - and then if still okay bottle and taste again, that should be a good way to determine whether or not its contaminated right?  I know it's not exact but from what I've read contaminated beer should be fairly obvious when tasting?

maybe maybe not. the yeast are going to be out competing the bacteria at first. it's only when all the easily metabolized sugars are exhausted and the yeast go dormant that the other, less particular organisms will begin to really show themselves. That being said, it could happen fairly quickly and it will be obvious.

just remember, if you get to a finish (stable gravity) and bottle that contamination could still take hold in the bottle and some organisms will create co2 while they work just like yeast. that can cause bottles to explode eventually so monitor and refrigerate after the desired level of carbonation is achieved.

[james_cornell]

would it better once I get a stable gravity, to wait before bottling? keep an eye on it?

[Stevie]

would it better once I get a stable gravity, to wait before bottling? keep an eye on it?

Yes, don't bottle until you know it is done. Most will measure once it appears to be done and again a few days later. If the number matches, it's done.

[james_cornell]

I meant more, after I've taken a couple matching readings, letting it sit for a week more or so before bottling to see if after the yeast goes dormant other organisms don't show themselves, like morticaixavier said they might.

Im assuming you get stable gravity once the yeast is dormant right?

[Stevie]

I meant more, after I've taken a couple matching readings, letting it sit for a week more or so before bottling to see if after the yeast goes dormant other organisms don't show themselves, like morticaixavier said they might.

Im assuming you get stable gravity once the yeast is dormant right?

Yep. In some cases it can take longer for an infection to show. Honestly, I'm betting you are a-ok