I just beat Fallout 1 and wanted to try out the sequel, but it's frustrating already. I am still in Arroyo and have to rescue this dog in a place full with geckos. The problem is that i am getting attacked by the geckos on sight even though every walkthrough or guide says, they will ignore me as long as i don't attack them. Since i only have a knife and most attacks miss, i'm getting killed pretty fast. Is this some sort of bug or am i doing something wrong? Fallout 1 was sometimes challenging, but this is just impossible.

My preferred way of dealing with the geckos is to leave that mini-quest alone and come back after getting a gun (assuming you have small guns tagged).

I think you can avoid em but its pretty hard

Trick in fighting geckos (and other animals) is to have a decent amount of action points.

Basically hit, then move away as far as you can. Gecko will spend all or most of it's action in chasing you and either not attack or attacks only once. Fight them one by one, sleep, eat or use healing powder between the fights.

But if you're not good at melee or unarmed, this might be impossible at this stage.
You can also get your hands on a sharpened spear at arryo. Much better than knife.

What Jarmo said + savescum like crazy.

Already tried that, but it seems, they have more action points than me and they are quite fast. I saw videos on YouTube where people walked right past them, while i get detected from a long distance. I guess, i come back later to them when i have a gun because my melee skill is too lame. Thanks everyone for the help.

Avoid them. Try and keep out of line of sight. You can get by not fighting any if you time it right and save at the right points.

You can "cheat" to get near Smoke without being spotted by Geckos.
As soon as you enter the map, start combat ("A" key), then spend your APs moving to Smoke. When you're out of action points, the combat will end, at this moment you have to press "A" really fast. If you did it right, the combat will start again, and you'll be able to move some more without being noticed. Keep doing this until you're in front of the dog. See if it's following you, then do the same process to get out of there safely.

I've had this happen before as well, sometimes the geckos can get very aggressive. A couple of questions:

What does your build look like?
What time of day are you doing the quest?
What level are you?

I usually like to tag Unarmed or Melee, or Unarmed on my characters even if I plan to use guns because otherwise they may not live long enough to when you can get your hands on some good guns.

I find that sometimes that the geckos get more aggressive at night or in groups, although it is easier to sneak at night.

If you do the Temple of Trials right you can get your first level up part way through. You could do a few other quest and wait until you hit level 3 before actually going after Smoke.

Besides, Unarmed is fun! Much more developed than in Fallout 1.

Edit: Though I usually raise it later, training as much as possible under the masters in San Francisco. Then again, I can never resist the urge of sequence breaking.

I've only had that happen once to me. Just like Jarmo said hit and run tactics will win the day for you.

The Geckos are no longer a problem, since i have advanced a few levels and brought Sulik with me now. But here's another thing: I'm having a hard time making a reasonable amount of cash. I sold all the gecko hides and traded in some other junk, but it was barely enough to get ammo for the gun and some stimpaks. Gambling at the Den is not an option because my skill is too low, so what else can you do to get more money this early in the game?

Pick pockets.

Never gamble. Just isn't worth it. Run around the wastes, kill and loot from random encounters. Loot everything you can find, drawers, lockers etc.

Only a couple of the geckos in the Arroyo area are hostile initially, but if you are fighting near one of the neutral ones, they will join in. The best advice is to try to fight them one at a time, instead of all at once. Smoke can help a lot too, of course. Also, remember you can save in combat, so if you're really desperate you can reload after every miss to make sure you're always doing some damage.

For money, most of your cash in the early stages will be from dead raiders and such, and from drugs you can find lying around. Make a note of how much every item is worth, and determine whether an item's weight-to-value ratio makes it worth carrying around.