It must have been nice watching someone else being desperate to pee and cool you talked to her about it.

Car parks make good toilets. Plenty of hiding places and once you squat down you are invisible unless someone walks along that particular row.   Pick a spot a god way along the row then you can check nobody is approaching before you squat, Multi storey car park stairwells are another good one - especially in car parks with lifts/elevators where the stairs are used less.  Usually you find there are multiple staircases and most people use the one nearest to the shops, so if you go to one in a far corner you are unlikely to be disturbed and if you choose a higher floor you have even less foot traffic. Having said all that, your post said about being in plain sight, so that sounds like you want to pee discretely whilst being in view of people.  For these cases you need to position yourself naturally and be doing normal things as @Paulypeeps says.   Check your phone, read a book, look in your bag, eat or drink something.   Nobody will pay you any more attention that normal and you can pee at the same time.  Here are some ideas   If you wear a skirt, you can sit on a wall or the edge of a raised flower bed and pee down the backside of the wall with nobody seeing. In a park, you can kneel down on grass with your legs apart and look in a bag in front of you.  I have done this successfully in very public parks peeing out of the leg of my shorts but for ladies a suitably loose skirt would provide complete cover.   You could also sit on grass - particularly on a slight slope with your legs out in front of you and your skirt pulled out from under you. Squat down over a drain and tie shoe laces or fiddle with a buckle. If you want to be naughty then you could get on a bus with absorbent seats and again lift your skirt as you sit then pee slowly into the fabric seat. You could go in a pub and either wet a seat or scoot to the front of the seat and pee on the carpet, hidden by a table.  The noise in pubs is usually sufficient to hide any noise you make -especially if you pee slowly.      

I've done it at a target in the dressing room. I've taken some jeans that I didn't want each and peed in them a little, along with just sitting down on the little seat and letting it out. I got super hot from it and had to finish, then I wiped myself with one of the unwanted things. left me shivering afterward. I also once peed a tad on another target fitting room floor a bit and in some pajama pants. 

"It is by diet-pop, alone, I set my Bladder in motion. It is by flavors from Laboratories: my Pee-Gasms acquire speed; my garments acquire Wet-spots; the spots become a greeting! It is by diet-pop, alone, I set my Bladder in motion!" (original Parody version of the [non-canon] DUNE© Mentat-mantra, ©2018 IIRC by IdoPiddleSome2, under my actual name. All rights reserved. Selected lefts may be negotiable. No SciFi clergy were harmed in the crafting of this Parody. Some assembly required). But, seriously, it is indeed by diet-pop; alternating flavors seem to work better & I often use my Pee as a mixer (which tends to egg my playful Bladder on), noticeably. I recommend approaching that with a wee bit of caution; Pee may act as a mild laxative at times. Best regards, all.

Re: Pool Water Colors, I'll stand corrected. Can't really comment on whether I play (sneaking-in a Pool-Pee). Somehow my Prostate Infection in 2002 (& maybe the Induction-Burn-Therapy I received in 2004) did some interesting wiring tricks. Starting later in 2004 I noticed my Nipples & Aureola lighting-up (blushing &/or tumescense) to Tattle on my Playful Bladder. They did it "silently;" I was only aware of it visually; no sensation these newly assigned Piddle-Pilot-Lights were lit otherwise. I took little notice b/c I'm a guy; beyond snapping a few digital pics in case I later felt moved to investigate. But it occurred to me: if sneaking a Pool-Pee had been a thing for me, it woulda been time to quit, w/those things lighting up like brake-lights to give the alarm! The way my Exhibitionism interacts with my Pee-Love (and women to whom I'm attracted), I'd find it more interesting if those lights of mine started lighting up more often, with or without bona fide Urine Alarm (so I thought). About a day after my Bypass in 2019; still in the first recovery-area, I felt them go off & they were glowing! Was doing my "Birdbath" at the sink, suitably attired, & when they lit it was intense. They went from their usual shade of "nothing-to-see-here" pink, to a shade of Genital-purple I'd never seen them do; standing out as if something unseen was pulling them. So now they don't Tattle secretly any more & my late Wife found it "cute." So I'm inclined to look forward to what's next vice worrying. Wonder if anyone has ever pranked a pool w/food-coloring...