How do you know when mulched pots need water?

I've got a bunch of potted peppers, and I'm not really sure when to water them since I no longer can see how wet the soil is without digging through the mulch. Any ideas on how to do this easily?

Thanks.

Here are some pictures (it just started raining before I took them; please excuse the weeds—kudos if you can identify what species they are; the borage is not a weed):