outdoor screws

Use "deck screws".

They are coated with a rust-resistant material.

Of course, that makes sense. Thank you!

is another alternative. They're sold with the deck screws.

Most zinc-coated fasteners don't have thick enough coatings. You have to look for "triple dipped" or something. Deck screws and stainless both would work. If the heads are visible, I'd usually prefer stainless.

Table joints get stresses from more directions than decks. I suggest considering (stainless) washers under the screw heads to help keep the joints tight in the table.

I may try using pocket holes to put the top together. I just used the Kreg for the first time on a project and it was pretty incredible how much faster things went with the pocket hole approach. I'll have to see if I can find stainless or deck screws for pocket holes that are not too pricey - anyone have a source? I have seen the Kreg blue exterior screws, but I'd like to find a cheaper option.

Then I was thinking of using bolts for the legs so that I can take it apart if needed in the future.

Are a lot cheaper if you buy them from Rockler or a similar online supplier. There's no need to buy the Kreg brand, so long as the bottom of the screw head is flat like the step in the drill bit.

If you're like to use a more traditionally profiled wood screw you can also buy a stepped drill bit from Lee Valley that has the same angle. Wood screws have the advantage that they have a bit of a straight section near the top, which keeps the screws from trying to push the two pieces of wood apart.

I forgot to mention that if you're interested in being able to take it apart, you should look at a part called a Hanger Bolt. One end if a course threaded wood screw that you put into the leg. The other is a threaded bolt shaft that sticks out, and you fasten down with a washer and nut (I like to use wing nuts to reduce my need for a wrench). That way you get the convenience of bolts without the ugly bolt heads sticking out. I built a table this way and loved it.

Thanks! I did find non-Kreg pocket hole screws at Rockler before, at your suggestion I believe, but I wasn't sure about the availability of stainless. With some googling, it looks like Kreg brand are the most common but I did find some non-Kregs at McFeeley's. The stainless are all expensive, though! It may be that the Kreg Blue-Kote are the better option - about $6 for 100 vs. $18-20 for 100 stainless of whichever brand. At least that's what my search attempts are coming up with!

The Lee Valley bit sounds like it would open up more options - I have definitely seen more flat-head screw choices. Will check that out, too.

Thanks for the tip about hanger bolts, too - that is exactly what I was thinking of but I didn't know the correct term.

Galvenized screws are a great low cost alternative and will never rust.They work great for outdoor projects
Hope this helps