Cucamonga-Guasti Regional Park
150 acres and two fishing lakes in Ontario — with a closed swim lagoon and an algae advisory you should know about.
Cucamonga-Guasti Regional Park is 150 acres just over the Ontario line with two fishing lakes, a playground, and a splash pad that is open and doing brisk business in summer. Hours run 7:30am to 8pm daily; entry is per vehicle — $10 weekdays, $15 weekends, $20 holidays — or $3 if you walk in, plus $1 per dog.
Now the part other listings soft-pedal: the swim lagoon is closed until further notice, and the lakes are under an algae 'Caution' advisory. Plainly — don't plan on swimming, and keep kids and dogs out of the lake water. The splash pad is the safe water fun here.
With those expectations set, it's still a solid cheap day out: real acreage, two lakes to walk around, and a playground that earns its keep.
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