Can I connect a water hose to an irrigation system?
I'm actually wanting to do this myself. I've looked into it for quite awhile. There is one video on youtube that is amazing. His system has been up for nearly 5 years without any problems. I'm at work and cant search youtube, but if you look up "150$ diy irrigation system" you will find it. 

Some things to consider.
 1. Water pressure from the garden hose won't be able to support more than 1 (maybe 2) sprinklers at a time. Depending on the type and GPM you get at your house. Test this with a 5 gallon bucket, I'm able to run one rotor 50ft throw and 2 very tiny low pressure nozzles at the same time.  


If The larger pipe or hose you use, the more pressure you get. I just bought 1 inch irrigation hose with an adapter to 3/4 inch for the sprinkler. I have a smaller yard, so I can get about 90% of the yard with one 50ft throw sprinkler. The smaller the diameter of the main, and hose the lower GPM you will have.  


Edit 
Okay for people who think smaller water pipes will increase water pressure, no. It's about fiction, volume and speed. Below is a great read about it, with some quotes.

https://www.irrigationtutorials.com/using-a-smaller-pipe-to-increase-water-pressure/  


  Grab your thinking caps for this.  As you well know, Bernoulli’s Principle essentially says (paraphrased) that as the speed of a fluid increases, the pressure of that fluid decreases. 
  
  Obviously as you force a given amount of water through a smaller size pipe, the velocity of the water must increase for it to get through the smaller pipe.  According to Bernoulli’s Principle that will decrease the water pressure!  This is called the Venturi effect.  By suddenly forcing the water through a narrow passage you can actually create enough of a pressure decrease that it creates suction.  This is how many fertilizer injectors work.  It also is another reason why using a smaller pipe would not increase the pressure– it would actually decrease it!