I would call the local Master Gardeners club and ask them for advice (or if there is a locally-owned nursery, you could go there and ask). The thing is, here in central CA where I live, a rosemary or lavender plant would do great in full afternoon sun - but I live in a different climate zone than you do. There are a lot of things that flourish in a semi-arid climate like mine that would die in a week where you live, and vice versa.
But, your local Master Gardeners will almost certainly have a staffed help line and/or email address, and they know what plants will do well where you live. They are a wonderful resource and love to talk about gardening -they are all volunteers and will not make you feel silly for not knowing. My mom has been a master gardener for years, which is how I know this!
One thing she has always told me is this: it's not that you're not good at gardening, it's that you're picking the wrong plants. The right plants will love where you've planted them (for instance, you don't want to plant a hydrangea there in the full afternoon sun, but a rose will love it there). If you aren't good at remembering to water, you need to pick plants that are drought tolerant. If you love flowers, don't plant a juniper. If you're deathly afraid of bees, then by all means, juniper is the way to go since it will not flower and attract them.
Anyhow, Master Gardeners! Call them, they're great! =)
