I dont' know if I should water or not water my shrubs/plants?
Hydrangeas are like the canary in the coal mine for drought/dry soil. They will wilt when the soil is dry long before other trees or shrubs show symptoms of lack of water. Your hydrangeas are very wilted. Water immediately.
Watering has to be tailored to your location and your plants. Sandy soil drains so quickly that it does not hold water well and, consequently, you must water more. Clay soil has particles that are so tiny that it takes longer for water to soak in, but once it gets wet it hold moisture longer.
Check and see what kind of soil you have.
Plant like soil that is about as moist as a lightly wrung out sponge. Once they are established (about 2 years) they like about 1" of rain a week, but by then they can tolerate less rain in short droughts.
For now, those plants need about a two gallon bucket worth of water--per week--or more. If you are using a hose, you need to figure out how long to run it to equal at least that much. The way you do that is to fill a bucket while you count. Then you know that if you apply the hose to the shrub/tree and count that long, the tree is getting that amount of water.
Trees and shrubs do not need to be watered when we get enough rainfall. The only way to know if your plants are getting enough rain is to use a rain gauge. A tin can can do the job, but you need to know what's happening on your property. You can't rely on weather reports.
Here is our website's watering tips: http://extension.umd.edu/hgic/watering-guidelines