A. A dining spot on the beach, where Dexter & Debra are seen eating tacos.

Q. Where is it supposed to be on the show?

A. In Miami.

Q. When did we see it on the show?

A. In Episode 11 (of Season 1), "Truth Be Told".  We see Dexter and Debra sitting at a table in some tropical-looking outdoor cafe, facing each other, eating tacos.  In the background, we can see the beach and a shoreline across the bay.

Deb tells him that she is upset trying to understand her boyfriend's intentions, and just then that boyfriend (Rudy) "coincidentally" shows up at the table and Debra conveniently has to go, leaving the two alone.  It's clear that she's hoping that Dexter can find out what Rudy is thinking.

Dexter notices there is a cut on Rudy's lip. Rudy tells him it was "a workshop accident this morning", but Dexter mentions that "it doesn't look like it happened this morning, it's already closing up". Rudy changes his story to "yesterday morning".

Dexter tells Rudy that his sister is falling for him, and Rudy tells Dexter that he is planning to propose to her. (Unfortunately, things don't work out very well for this couple...)

Q. What is it actually in real life?

A. A small concession stand at a beach park.

Q. Where can I find it in real life?

A. Right on the beach, it's called the Kayak Cafe, and is located in a small park called Bayshore Playground, located at 14 54th Place, in Long Beach, CA.

That's on "Bayshore Beach", on the east side of 54th Place, just north of E. Ocean Blvd, where the Long Beach peninsula joins the mainland - about a mile southeast of the Belmont Pier.

The small beach park includes a small cluster of sporting facilities, including a racquetball court, a basketball court, a roller hockey rink, handball courts, a paddle tennis court, playground equipment for kids, and a co-op pre-school. (During the summer months, they tend to close off (to traffic) the adjacent 54th Place & Bayshore Drive, to keep the kids safe who play at the park.

On the north edge of these sports courts, right on the sand (next to the handball court), there's a small, thatch-roofed bamboo structure where you can rent kayaks (at $10 an hour), that acts as a beach refreshment stand, selling snacks, great French fries & beverages. (They also do parties and weddings on the beach, by bringing in extra tables.) ( It somewhat resembles the tiki hut where you can buy pineapple juice outside of Disneyland's "Enchanted Tiki Room" - there are even a few carved tiki's sitting around the structure...)

They even have their own website at www.alfredosbeachclub.com/kayak.htm

The producers used the thatch-topped archway of this concession area to frame Dexter & Debra, added a table, pointed the camera out towards the blue Alamitos Bay, and made it look like a major beachside restaurant.

Here is an aerial photo of the beach area.  And here is a map link.

( This taco cafe/tiki hut, by the way, is right across the street from a key "Dexter" location: the villain's lair.
)

Q. How the heck did you figure out where it was?

A. I recognized the view as being Naples Island, and in the background, across the bay, I recognized one tall condo building (that stands out among the residential homes that make up most of the island). So, using aerial maps, I drew a sight-line from that condo, across the bay, to the beach to determine the approximate location. Then I visited the spot in person and found the same thatched archway seen on the show.