PJLS is quite affordable.
Was there from elementary 1 to advance.
They are quite good...but honestly, it really depends on the teacher.
I recommend my previous sensei...Cheng Sensei

Basically, as mentioned, depends on the sensei.
i have had 2 senseis.
first 1 was good, we are all made to read everything 3 times (lol) and randomly picked to make sentences.
she kinda retired due to health reasons after elementary 2.
next my sensei was cheng sensei which i think is the best (my wife thinks so too although she was nvr taught by her)
cheng sensei will make every student read (not 3 times but part/paragraphs equally) and also make sentences from the taught pattern from the text book (well, basically for me was intermediate 1 and 2 only)
conversation...basically, depends on sensei and you.
both my sensei spoke only in japanese, once we kinda get the hang of it except for some explanation when we look very lost.   
u can always speak to ur sensei and classmate in jap.
in between, i have had 2 replacement sensei taking over the class from time to time.
one of them somehow gave out a gloomy aura which made the class very boring (very bad condition to study) and the other nvr seems to write anything on the board but gives out a lot of notes to read.   
my wife also had 2 sensei...both were replacement sensei to mine when my first sensei could not make it on last minute.

yes, predominantly is mandarin.
but u can inform ur sensei that ur mandarin is    level...usually that is the first question the sensei will ask.
i had an english ed classmate...my wife is english ed too.

PJLS has a facebook page. You can "like" it if you want to subscribe to their updates on latest activities and classes.
Their standard course is based around the Minna no Nihongo syllabus, though different teachers may have different styles and reference additional material. And, yes for the amount of ground you can cover, PJLS is still one of the cheapest and value for money language schools in Penang.
I don't think there's anyone who teaches/learns the Japanese language in Penang who hasn't heard of Cheng-sensei 
All the teachers there are part timers with varying amounts of experience. Foong sensei is also very experienced and highly recommended. (I think he's the one who likes to make students make their own sentences )
It's a common misconception that everyone teaches in Mandarin there. Many of the teachers do use English or whatever it takes to get the point across

but generally I think you get the idea...very few people who start out learning japanese get to the point where they master functional use of it...
A real pity, considering it is one of the easier foreign languages to learn.

good luck on your journey
Also, everyone has a different way of learning, but dedication, enthusiasm and persistence are always common key elements. 1 year is a long time to get used to katakana and hiragana, btw
it took me whole of 2 weeks using flash cards to get to 80% proficiency. maybe you should try a different method from what you are using now...
Also, if you are relying on textbooks which are in romaji, PLEASE THROW THEM AWAY. They are an impediment to serious learning of the language.

I hope you didn't take it the wrong way 
What I meant was that basic hiragana and katakana is a prerequisite to be able to use the textbooks, especially if you are using books like Minna no Nihongo where there is nary a romanized word in sight. (there *is* a romaji version, but I would stay away from that). 2 to 4 weeks is par for the course for a beginner to be able to recognize 60-80% for the kana consistently

I'm just noting that if you are still have difficulty with those after one year, perhaps there was not enough emphasis on memorizing and writing drills in the beginning. In my experience, flash cards with a partner is the fastest way to recognize the kana, with writing drills to reinforce learning. There is a reason why most teachers spend an inordinate amount of time with the kana writing in the early part of the course: if they don't get it out of the way, the students will suffer later as they move deeper into the syllabus because the book assumes ability to read the kana already..