Yes, upland parks NOT in flood plains are fair game for me, too. I forage pounds and pounds of chanterelles from upland parks in the North DFW area, and serve them to guests at my restaurant, and gorge on them with friends and family.
The majority of morel findings in the metroplex are in floodplains of the Trinity River and its tributaries. Take a stroll through any of these and you will find as much garbage as there is greenery, and you know that all of the city's street runoff has gone through the gutters and sewers and ended up on top of that soil during floods.
My warning is specifically for floodplains, which tend to be where morels in the metroplex are found. (And the more urban you get, the more green space is concentrated only in floodplains, which do not offer viable commercial real estate.) You could not convince me to eat a single mushroom from an urban flood plain, morel or otherwise. But undisturbed upland parks that do not get submerged in street runoff are regular targets for my forays, and one of my garage freezers is absolutely full of mushrooms from these areas...boletes, oysters, chanties, and agarics.
Morels, in particular, are known to concentrate heavy metals in the soil. This is one reason why mushrooms are being researched for cleaning up toxic ocean oil spills. I seriously doubt that eating three or four of them found in LB Houston Park, for example, where I have found a few now and then, or along the White Rock Creek greenbelt, where larger finds have been reported, will hurt a body.
But you will find more if you get outside the city! And there is less worry about them being bad for you.