Hello duda -
Your Juniper will do fine outside in your area - Keep it there at all times but you will want to protect it from too much heat in the summer, especially the reflective heat from a wall. Move it into a partially shaded area when those temps get over 100+.
Your climate is quite good for a Juniper and they like dry heat and lots of sun. Be careful not to "over love" your tree by giving it too much water. This will kill off your poor tree faster than anything. If your tree is in a well draining soil, there is virtually no possibility of over watering here. I have my Junipers basically growing in lava rocks, sand, bark and baked clay. When I water, it takes but a second for the water to go out the bottom of the pot. Please be careful of giving your tree "wet feet". In fact, you may want to check out the condition of the roots either by repotting it now, or lift the tree out of the pot and look at them.
In this time in AZ (winter), I give it water about once a week or 10 days. In the summer, I water and mist once or twice a day. Pinch off those browning leaves as they wont grow back.
Here is a great picture from phoenixbonsai.com. You should check out the information they have there also about growing in your area.
Also, Baker Nursery in Phoenix has a somewhat large selection of bonsai and supplies.
I think it's okay for leaves of your Juniper to get some browning. It shouldn't be a source of stress. Keep it outside, please! You probably see a lot of Junipers in the landscaping around where you live.
If it's any consolation, I have basically given my Junipers less attention on purpose just to see how they would fare. They have done well in spite of the fact that I would have thought they needed to be watered.
If you could post a picture or two, it would be helpful. Also, let us know what kind of soil it's in and the condition of the roots.
Well, not much new info than what people have said. This is a great resource with a lot of knowledgeable people here. Please feel free to ask more.
HTH for starters..