A very popular spot in Ellensburg for smoking is the wild horse wind farm/whiskey dick mountain. It has a great view overlook the area and the sunset. It is very safe and private also. It also has a great view of 4 mountains plus E-burg, Royal/Quincy valleys, and vantage. Check it out. It’s a great spot!
There is just something about getting high outdoors and enjoying the great natural scenery that is around you. Well if you were looking for some cool places to do that here then you should check out Ellensburg Park, and Irene Rinehart Riverfront Park. These are two really great places with lots of great natural beauty that you should check out. Bring a bowl or a roll and you can have a great time smoking your good weed and chilling out for the afternoon. Who knows you may even bump into a few other like-minded stoners and be able to have a nice smoking session together with them.
If you look for a private place (not necessarily a pretty one) you can go behind Fred Meyer Grocery shop and you will find a private place to smoke weed in.The shop is in the western area of Ellensburg and east to the Rotary Park. Another place which is a bit better looking is the Wippel park also a bit to the east of Rotary Park, its a bit less private but you will have something to look at while smoking. Like you said there are a lot of parks but its not very hard to find a corner to smoke in privately. Good luck!