Planting can be done anytime of the year, but planting in the fall is one of the best times. Because of the temperatures in the fall, plants have a better chance at establishing roots before the following hot summer temperatures and possibly dry conditions. There is also less chance of shock to plants, especially when transplanting.
You may want to consider before planting, any of the needs of the plants themselves-water, how much sun/shade they are exposed to, if they will need general maintenance or are somewhat maintenance free, and how big will they get.
Whether you are planning on planting yourself or need assistance, let me know if there is anyway I can help. From the design to the install, I do it all!